Notice: We are in the process of migrating Oral History Interview metadata to this new version of our website.
During this migration, the following fields associated with interviews may be incomplete: Institutions, Additional Persons, and Subjects. Our Browse Subjects feature is also affected by this migration.
Please contact [email protected] with any feedback.
Photo courtesy of Bertram Batlogg
This transcript may not be quoted, reproduced or redistributed in whole or in part by any means except with the written permission of the American Institute of Physics.
This transcript is based on a tape-recorded interview deposited at the Center for History of Physics of the American Institute of Physics. The AIP's interviews have generally been transcribed from tape, edited by the interviewer for clarity, and then further edited by the interviewee. If this interview is important to you, you should consult earlier versions of the transcript or listen to the original tape. For many interviews, the AIP retains substantial files with further information about the interviewee and the interview itself. Please contact us for information about accessing these materials.
Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event. Disclaimer: This transcript was scanned from a typescript, introducing occasional spelling errors. The original typescript is available.
In footnotes or endnotes please cite AIP interviews like this:
Interview of Bertram Batlogg by David Zierler on May 14, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Interview with Bertram Batlogg, Professor Emeritus at ETH Zurich. Batlogg surveys his current interests in topological superconductivity and superconductivity in twisted layer graphene, and he connects this current research with his own work at Bell Labs earlier in his career. He considers the current state of play in high-Tc research and he recounts his family's Austrian heritage and his upbringing early interests in physics. Batlogg describes his undergraduate experience at ETH Zurich and his reasons for remaining to complete his PhD thesis work. He describes Bell Labs as the Mecca for his research as a postdoctoral fellow and then as a staff scientist. Batlogg discusses his work on Hall effect measurements, superconductivity, and heavy Fermions, and he describes his tenure as head of the solid state physics and materials research division. He describes the culture of basic science and how it changed from the 1980s to the 1990s, and he discusses his formative collaborations with Bob Cava and 1-2-3 YBCO. He narrates the story of meeting Jan Hendrik Schön and the issues that would lead to the investigation led by Mac Beasley. Batlogg conveys the scientific and emotional turmoil of this episode and the impact this episode had on his sense of trust in people. He describes participating in the investigation after he had already left Bell Labs to return to ETH Zurich to build up a research group with a focus that included topics such as charge dynamics and heavy Fermions in very high magnetic fields. At the end of the interview, Batlogg emphasizes advances in data acquisition and spectroscopy that propelled the field forward over his career, and he considers how some his research can contribute in the future to discoveries in both the applied and basic realms of science.
This is David Zierler, oral historian for the American Institute of Physics. It is May 14th, 2021. I'm delighted to be here with Dr. Bertram Batlogg. Bertram, it’s great to see you. Thank you for joining me today.
My pleasure. Wonderful to meet you.
Thank you so much, Bertram. To start, would you please tell me your current title and institutional affiliation?
Yes. I'm now Professor Emeritus at ETH Zürich, since my compulsory retirement at age 65, in 2016. Not “eremitus,” which would mean hermit. So it’s good not to mix up the letters there. I'm not a hermit!
Until shortly before the pandemic hit, I was still teaching my favorite course at ETH, which is Physics in the Smartphone. Since then, I'm involved in two large scholarship organizations at ETH. One is the Excellence Scholarship & Opportunity Program, the other Society in Science – The Branco Weiss Fellowship Program for exceptionally qualified researchers worldwide. Therefore I'm quite frequently at ETH.
On the other hand, I'm also serving on the board of the University of Applied Sciences in Dornbirn, Austria, a public institution with more than twenty different Bachelor and Masters programs. And in addition to that, with my wife we do enjoy outdoors life, skiing, mountaineering, and mountain biking as well. And many other activities, including work for a social institution. So I'm in a very good place right now.
Bertram, beyond your own field of research, what’s currently interesting to you in physics right now? What are some of the stories or experiments or topics that you've been following lately?
Well, I must admit that I don’t read the literature every week anymore, as I used to do in the past. On one hand I've found the development of topological states in condensed matter interesting, including topological superconductivity. Superconductivity in twisted bilayer graphene with some similarity to the cuprate phase diagram is also fascinating, and I'm also impressed by the high pressure-induced superconductivity, now at room temperature, in some hydrogen-rich compounds. These developments actually brought me back to my own early days at Bell Labs, when I also had in mind, but soon gave up because of technical difficulties, to produce metallic hydrogen, stimulated by predictions by Neil Ashcroft, who passed on just a few months ago. These are examples of areas which I particularly find interesting to follow right now.
Bertram, a very broad question that I think will punctuate much of our discussion, and that is, in your fields, the interplay between theory and experimentation? In broad brush strokes, when over the course of your career has theory provided the leading guidance to experimentation, and when have the experimenters really pushed theory forward?
Well, that’s a broad question. Most of the times, when a so-called “first paper in a chapter” was written, it was rather the experimentalists hitting upon a gold vein or being just lucky or having had a good intuition, that started the field off. However, I must say that several studies were clearly guided by theoretical thinking. For instance, in the study of unusual superconductivity. The mechanism that leads to unusual superconductivity often produces pairing states with gap functions that have zeroes at points or along lines on the Fermi surface, which means also that the temperature-dependence of particular properties below Tc follow power laws. These guidances in the field of heavy fermion superconductors in particular, and in cuprates later on as well, led us into particular directions of experiments.
So we tried to do experiments such as ultrasound absorption, just to show whether or not such power laws did exist. That’s an example of being guided in experiment by some theoretical considerations. Earlier on during my doctoral thesis times, our discovery of a magnetic ground state in intermediate-valent TmSe had confirmed a prediction by Chandra Varma. In a broader sense, Alex Müller and Georg Bednorz were also guided by a working hypothesis, when they discovered cuprate high temperature superconductivity.
Bertram, I'm curious the nomenclature issue. Where do you see the distinction between solid state physics and condensed matter physics as a matter of chronology, and as a matter of actual scientific distinction?
[laughs] Oh, I'm laughing. The first answer, it is a matter of age. [laugh] What I meant to say, if you just look at the history within the American Physical Society, it used to start out to be condensed matter physics, periodic arrangements of atoms and electronic properties thereof, and so on. And so it was about solids. Condensed matter was an expansion that was most appropriate and necessary, because there was so much rich physics to be found in other forms of condensed matter. If I'm using condensed matter physics, then it is in order to describe some, I would state, large organizational thinking. If I talk about solid state physics, then it refers to what I am doing myself in the laboratory. I don’t want to grade anything. And I hope we understand the differences between them. In the 1990s as a Councilor of the APS Division of Condensed Matter DCMP I was fully exposed to the rich spectrum of condensed matter physics when the March Meeting program had to be organized.
Do you see the mysteries of high-temperature superconductivity essentially the same today as when high-Tc was discovered?
They are not the same, but they are just as fascinating. Today we have an enormously more detailed knowledge—I wouldn't say full understanding, but knowledge—of how electrons behave in these materials. Highly developed, sophisticated, experiments unimaginable in early days, provide detailed insights and point to challenges to develop an all-encompassing understanding. So it is just as fascinating today as it used to be in the early years.
But the level of understanding—the level of uncertainty—or I'll put it differently—the level where we still are not clear is at least orders of magnitude higher. People were very simpleminded, because a Tc of 90 degrees by itself was just extraordinary. The mystery manifested itself immediately after we had made single phase YBCO, because the Tc of 90K is about an order of magnitude higher than in other superconductors with the same density of electronic states at the Fermi level. This was one of the key insights we reported at the “Woodstock of Physics” at the March Meeting in 1987. Then came the isotope effect result, where we replaced O16 by heavier O18, showed by Raman spectroscopy the expected reduction of the phonon frequencies, but found essentially not shift in Tc. These were strong indications of novel physics.
Shortly thereafter we realized that something very peculiar is going on in the cuprate superconductors, indeed, because there is a generic phase diagram that describes the various electronic states, including superconductivity, when the electron density is varied by modifications of the chemical composition.
There were these unusual temperature dependencies of the resistivity. There was the so-called underdoped range with —the first language for that was a “spin gap”, later also “Charge gap”. Nowadays, we know why they come about, and how they are connected on a much deeper level, and so on. So this phase diagram issue at the beginning was fascinating, but now we have a much more detailed knowledge that makes us think on a different level.
What you're saying, Bertram, then, is that with high-Tc, it follows the Socratic principle where the more we know we don’t know, the more we don’t even understand what we don’t even know.
[laugh] Well, at some point, it feels like that. And I hope there will be a time when we can say, “Yes, that is what is going on.” Rather than having all the details laying on the table, that we see how they all perfectly, from first principles in quote, fit together. I would like to quote myself - was it in 1987? - “I think we have all the theories, except we don’t know which one is the right one.” [laugh]
I think I was quoted in that [laugh] in a Physics Today article one day, and I got lots of heat for that. [laugh]
Or relatedly, what I heard is, you can fudge the theory; you cannot fudge the data.
[laugh] Well, watch out.
That would bring us to a different chapter that we don’t want to dwell too much on.
That’s right, that’s right. Bertram, in what ways has discussions over applications of high-Tc changed over the years? In other words, what you're saying is that for basic science, there has been a tremendous value in terms of what we understand now versus what we understood 30, 40 years ago. But in what ways have discussions about applications that have actual scientific value, with regard to high-Tc, how have those discussions changed over your career?
Well, these are old stories. At the very beginning, everybody was excited about just the high temperature itself, the scale itself. Very rapidly on, very early on, and it was partly work with Thom Palstra at Bell Labs, when we realized that the dissipative vortex motion in these materials is an issue. It means that in a high magnetic field the electrical conductivity of the superconductor is not better than that of a copper wire. It strongly depends on the orientation of the field with respect to the crystal. This disillusionment came quite early on, realizing that these superconductors are essentially two-dimensional, depending on the details of the materials. So it was clear that one would have to choose particular compounds where this anisotropy was the least impediment.
The bismuth copper oxides therefore were not high on the list of candidates. YBCO or the Y123 compound, however, was more promising. And so it depends what kind of application we were thinking about. Cables or electronic components. We had been working at Bell Labs in collaboration with Lincoln Labs and other institutions in the Consortium for Superconducting Electronics —we had been exploring, among other things, the use of thin film superconductors for microwave filters. That actually turned out to be a valuable application for cellular telephone networks.
At the end, I think it was the cost factor that made it not a big commercial success. Technically, however, it was perfectly fine, meaning the superconducting microwave filters, particularly for wireless communication. They have the advantage that the flanks of the band pass filter are much steeper than in traditional filters. Therefore, one can use the allocated frequency band more effectively, more information can be transmitted. And we demonstrated that, and actually that worked out very well. So this application in the form of a thin film on a substrate worked out very well. It did not make it to the market in large scale. There are some applications, as I understand, but not in large scale, because of the cost associated with that. So that’s one side.
The other side of making wires is an entirely more challenging enterprise, because one has to have large quantities, properly oriented grains, not breaking apart. One has the problem of grain boundaries not being very good junctions between grains, and so on. Companies had been working for long, long while. Several demonstration projects had been made in various places in the world. After a successful 1 km demo project in Essen, Germany, a 12 km application is being planned for Munich. In addition, research magnets involving cuprate superconductors are also being produced. Applications in wind turbines are also explored, mainly as a mean to reduce weight. As the emphasis on energy saving becomes more pronounced, we might see more applications of superconductors.
Bertram, let’s take it all the way back to the beginning. Let’s start first with your parents. Tell me about them and where they're from.
Well, my parents are both from Austria, from the westernmost part of Austria, a small state named Vorarlberg. Mom and dad lived in this mountainous area. My dad was one of five children. His father was a small farmer who also worked in a local hydroelectric power plant to earn some money. And he was, smile or not, he was mayor of the small village with about 150 people living there. There was no income associated with that; it was just fame, in quotes, and it was service to the community. We three children also grew up there. The village is known to be well protected from the sun. [laugh] It is on the wrong side of the valley and does not get much sunshine because it’s too close to the steep mountain cliffs.
[laugh] What languages were spoken in this village?
It is the local German, which is a language close to the language spoken in the southern part of Germany, and also in nearby Switzerland. It is distinctly different, language-wise, from languages and dialects spoken in the rest of Austria. This part of Austria is very small, about 2,600 square kilometers, with about 400,000 people living there now. And they are also geographically sort of separated from the rest of Austria by a high mountain ridge, always oriented towards Switzerland and Germany.
The languages are very interesting. I'm interested about those things, because in those days, before the mobility of people was not as high as it is today, we could spot people—we could locate people by the details of the language, down to about two or three miles. People in the same valley, two miles further up, spoke a slightly different dialect. You could hear them. And I found it just amazing how languages had developed over the centuries so they could be distinct on the level that one can hear the differences so easily. Not just the vocabulary; that was one part. But also the way of pronunciation. It’s a very strong accent, which I could never get rid of.
And then you asked about parents, yes. Let me just tell you more about them. My father was a mechanical engineer, and he had for all his life worked at the same textile manufacturing company. This company employed about 2,000 people in a little town of about 10,000 people. So it was by far the dominant employer, and I'll come back to that in a second. He was very much also a hands-on person, in addition to a designer. Fire prevention is of utmost importance in a textile factory, because of all the dust that’s around, he also was the chief of the fire department in that factory for more than 40 years. And he also was, on the side, the chief of all factory fire brigades in the state. All was volunteer work. Dad was on the road in the evenings, on the weekends, always in his fire fighter uniform, having some official function here and there. He had lots of gold on his shoulders and medals of recognition on the uniform. Our dad was a dedicated volunteer man.
Did your mother work outside the home?
Yes, she did. Mom worked in an administrative function outside the home. But then when the three of us joined the family, she stayed at home, was a wonderful housewife, a dedicated mother. She put lunch on the table at a quarter past twelve, because that’s when we came back from school every day. Our father also came for lunch, by bicycle. So it was a very traditional family life.
I think because both of my parents had to serve in World War II and had seen the horrors – they wanted us to grow up differently. They wanted us to believe in the goodness of people, to respect people, and to trust them. And that was the basic philosophy in our family—unspoken, but it was just the way they tried to raise us three children, in a protected, in a loving environment. Because when they were young people, they had seen the worst of mankind. I think my two sisters and I still carry this basic positive and optimistic attitude in us, in our lives. And our parents have passed on long time ago, but that’s what they have left us.
You say they saw atrocities. What were their experiences specifically during World War II?
Of course, as you hear from many other people as well, they tried not to dwell on the details, because they just didn't want to talk about it. But what I understand, my father was in the German Air Force. As Austrian, he had to serve in the German military, of course. He was flying fighter airplanes, actually. And then at the very end, he ended up with ground forces on the Russian Front, where he saw almost hand-to-hand battles and atrocities of the worst kind. He saw killings, short-range killings. He never told us the details of it, but that’s what I have learned from him. And he almost died of hunger as a POW when he was in France for a long time. So these people, they were sort of broken. And I understand that they managed to come back and raise families, and build a house, and try to forget about these horrors that they had to live through in their early twenties. So I have high respect for them and for many others of their generation.
Bertram, did your father ever express any moral misgivings, fighting for Hitler’s Germany?
They had no choice, Austria had become part of the German Reich. Either you join the military—it’s a compulsory draft—or they put you on the wall and you are shot. My father hated serving in the military. Oh, yes! Enormously! His father lost all his jobs because they were adamantly opposing the Nazi regime. So it’s not a matter of choice; it’s a matter of how can you survive that. I mean, at every opportunity, they despised this Nazi regime. Particularly also in our area, there was lots of opposition to it.
In your family’s experience during World War II, do you know if they knew Jewish families? Were they aware of what was happening to the Jews during the war, in Austria?
I don’t know how much they knew about it, because—well, put it differently. They knew that horrible things had happened, because a little bit down the valley, about 20 miles from where they grew up, there was a town with a Jewish community. Its name is Hohenems, and it had a wonderful centuries-and-centuries-old culture of Jewish people living there. There’s a big Jewish cemetery there, a museum, and stately houses. We go there regularly to look at it. So they knew that there were Jewish people in their neighborhood, and they all had disappeared. And they knew that something horrible must have happened to them.
Yes, they did know that. I think that they were not aware probably of all the details that we know nowadays. And they had seen what happened to transportation of Jewish people to the concentration camps and so on. I think this was all part of their horrible experiences they had to go through as young people.
Bertram, as a young boy, born five years after the war, do you have any early memories of the devastation of the war? Or where you grew up was not that badly harmed?
Oh, sure, I do have memories, because Austria was occupied for ten years, until 1955, by the four victorious powers—Soviet Union, America, France, and Britain. Austria was divided up in four sectors, and our region was occupied by French troops. Almost every day I saw the French troops walking by in front of our house.
One day, I remember, these poor guys, the soldiers, had to march with the gas masks on. They looked like elephants, because they had this huge tube connecting the face mask with the filter pack on their hips. Of course, they were very friendly. But the presence of the occupying forces was almost a daily experience.
Coming back to the devastation. Our area was not very much affected, as it was not part of the battle front. Except for the very last days of the war, when crazy hard-core Nazi troops retreated in the mountains and tried to fight the advancing French troops. A few bridges got damaged. However, there was one major horrible event. Earlier, in October of 1943, fifteen US Flying Fortresses could not reach their target in Germany, and when they returned towards south they dropped some 36 bombs onto the small town of Feldkirch at the border to Switzerland. A school building and a makeshift military hospital were destroyed, and some 200 people lost their life, including about 100 schoolgirls. That’s devastation.
But in Vienna, for instance, and if you look at old pictures, it’s just heartbreaking to see the devastation and what people had to go through. And if you go to Vienna now, which I would recommend you do one of these days, it is spectacularly wonderful. They’ve rebuilt it, and now it’s one of the most wonderful places in the world. It just goes to show what people can reconstruct and can redo if the economic situation allows it. In this case, the Marshall Plan was a big help.
Let’s return back to textiles. What more did you want to add?
I had mentioned that this factory employed about 2,000 people out of 10,000. People came also from nearly villages. But then, in the 1980s, the textile industry completely collapsed, because of the cheap imports from the eastern countries. The textile industry contributed more than 70% to the total industrial value created. Nowadays, this fraction has dropped to some 5%. It sounds like a major disaster with job losses. But, somehow new companies started making high-tech stuff, mainly metal-based manufacturing.
And I’d like to mention three companies that became leaders in their own fields, in addition to many small companies. One company manufactures equipment to produce plastic containers. I've visited them several times. They develop and produce extremely high-tech machines to fabricate all kinds of plastic containers for consumer products, such as ketchup, liquid detergent, and so on. Anything that you hold in your hands in the grocery store, anywhere in the world, has a good chance that it is being produced by this company. That was one example.
The other one is a world-leading cable car and ski lift company. Perhaps you have recently seen pictures of La Paz in Bolivia or Mexico City, where the public transportation nowadays goes by aerial tramways. Or the gondola at Whistler Mountain, British Colombia. And the third example I would like to mention is just down the valley—if I look out my window now down the valley down, I can see the plant. Remarkably, it’s the only company in the world that bottles the energy drink that gives you wings. Don’t get me wrong; I've never finished a whole can!
It is so horrible; I can’t even smell it. But this company bottles at two plants each and every Red Bull can that’s being sold worldwide! Approximately eight billion cans a year. The technology and engineering behind this number is amazing and very impressive. They produce more than 100 cans a second, which is about four times as much as submachine gun shoots bullets.
Twenty-four hours, seven days a week, 350 days a year. Imagine what it means to produce these cans on site from bulk aluminum down to the final painted can. The whole logistics of transporting stuff there and transporting it away! Every day, they have a huge train leaving the plant with containers to go all over the world. So I mention it only because these are sort of the extreme examples of how the economic structure can change in a short time, if it’s combined with high tech, and all the science that’s behind it, of course. So I just mention it because it is such an impressive way of witnessing high-tech stuff popping out of the ground. And all three examples are family-run businesses, with multi-billion yearly revenues.
Not big MBA-run corporations.
[laugh] That’s great.
As a boy growing up in Austria, in the middle of divided Cold War Europe, if heaven forbid there was an outbreak, a land invasion, a World War III during the Cold War, who would you have viewed as the bad guys? Would it have been the Americans or the Soviets?
Come on! That’s an obvious answer. We have been informed by the older generation in the proper direction. Not only that, [laugh]—well, depending on how we want to go about it—I can tell you that particular story, or we can go through my preschool and school years, so we have a little bit more stuff to talk about.
We'll go back to preschool. Let me hear this first.
Just let me tell you that I did have good personal reasons to hate the Soviet troops. They invaded Czechoslovakia in 1968, just when I was in the compulsory military service in Austria. We were put on high alert, and I was not allowed to go home on the weekends to see my girlfriend.
That’s why I disliked them. [laugh] Enough said. Yes.
Let’s go back to your early schooling. What kinds of schools did you go to as a young boy?
Of course, we only know public schools here, which are good. My first grade in grammar school was in a single-room school, where in one room all eight grades [laugh] in this small village had been educated. There was one teacher for all of us. In hindsight he was a spectacular teacher, multitasking, better than we can learn in any university courses. And he just had it. He was a most impressive man, who actually was also a teacher of my father’s way back.
He was an authority in the village. The children came from small farms that only had a few cows and a few pigs, perhaps a horse or two. So we had a very good first-grade education. What we did not need was sports, because sports was what we did as soon as we left the building. I do remember that in those days and before that, I already got my first pair of skis, as it is typical in this area. And I had my first experience doing sort of chemistry or physics, because on wooden skis, you need to put some wax on the bottom so that they would glide on the snow. As a young boy I was experimenting with an old iron from my mom, what wax, what kind of paraffin, would be the best. All Christmas tree candles in different colors, were molten to figure out what would become the best glider. That was my early experience with a little bit of chemistry or physics surface grinding, in those days. Hands-on, I would call it. In those days I was already interested in observing the trees and little creatures in our back yard. Mice and bugs. I was digging up worms to dissect them. Observing nature and trying to figure out how things work started early.
And then after the first year, our parents built a home in a nearby town where my father worked. It is a center of many schools, where students from all the five valleys that joined at that place come together. So we did have a very good grade school where I attended second, third, and fourth grade. There was one excellent, tough, but very good teacher. The first thing we had to do every morning, for ten minutes, was calculations in our head. He would just challenge us—say, “Two plus five plus seven divided by seven — David, what’s the answer?” So he would wake us up every day this way. And I think that left a lasting impression. Concentrating and using our head to do some simple arithmetic was very helpful.
From then on, I went to what’s called the gymnasium. It’s similar to a high school, except it’s organized differently. Our class was very small, some 25 students only. Fourteen girls, eleven boys. We had a wonderful class life, and we stayed together all the years. Just recently we celebrated our 50th graduation anniversary. We were just as happy together as we were 50 years ago. Several of the teachers, including in physics and in chemistry, were excellent.
Perhaps I should tell you a story about the physics teacher. There were no advanced courses, just one type of course. And we only had two lessons of chemistry and two of physics per week. Learning was intense. The first physics teacher was a senior person, close to retirement. And he adopted me as his teaching assistant, something which is unusual in high school, of course. But I was allowed to come in the day before lectures and help him set up the demonstration experiments that he would show us the next day. This way I learned a lot about physics and how to do physics, literally behind the scenes.
And then in the last two years, a freshly graduated young man came, very nice, dynamic and energetic. Gerhard Blaickner quickly became our favorite teacher. And he also adopted me as his physics TA. One afternoon I realized that experience and craftsmanship make a difference. The teacher and I were trying to set up an experiment—it was a simple electronic circuit. But the oscilloscope didn’t show what was expected. The signal was jumping around, it was noisy, garbage. Yet we were sure we were following the instructions. After an hour or two of us fiddling around the old teacher walked by, realized that we had problems, and he said, “Oh, you guys, all you have to do is just—you put a high impedance resistor across the oscilloscope input.” Which we did, and lo and behold, we had the cleanest signal that we could ask for.
The bottom line of the story is, the old man knew that in reality you have to deal with noise. And so at that point, I realized that real-life experience also makes a big difference, not just knowing the theoretical details. It was a good lesson learned there.
Blaickner was a good teacher, and at the final formal exam, I remember he asked me about the basic theory on electrons in an atom. This was quite an advanced topic for high school. And the examination team—including also several external teachers—was quite impressed when I explained the spectral lines series in the hydrogen atom. And I still remember the Lyman, Balmer, Paschen Brackett, and Pfund series—one over n squared minus one over n two squares. And so I was off to a good start into physics.
While that was it in terms of the formal education, I think what formed me much more was what I did on the side. The grades were good, decent, but I didn't care too much about the school, about Latin, and other languages. We had an outstanding philosophy, German and history teacher who had a big influence on our class. But I learned most of the physics and chemistry stuff outside school, at home with my hobbies. If you are interested, I'll tell you those stories.
You mean hobbies including physics?
What was the environment that led me to do physics? In our basement, our father had a wonderful work room with lots of tools. Many afternoons I spent there. As a small boy I got an electric model railroad kit for Christmas. While I liked it a lot, its lasting impact was that I could use the transformer and the power supply for all kinds of electrical experiments. Among other things, I was doing electrolysis of water, producing hydrogen and oxygen out of water. And you know what you do with that, of course—you let them explosively react afterwards. So it was really always fun to do things.
In school we had what nowadays you would perhaps call advanced show-and-tell. Our children in New Jersey were doing show-and-tell every week. We did it perhaps once or twice a year which meant we gave a presentation for some 15 minutes on a topic of our choice—literature, history, geography. Physics or engineering were my choice.
Once I was trying to explain to my fellow students how bricks are being made. Because one of my uncles had a brick factory. Not the concrete bricks, but the ones that are made out of loam or clay. I learned from my uncle how these wonderful yellowish bricks are produced. How first to extrude them, then to dry and put them in the kiln to burn them. That was one of the topics, because that large-scale engineering processing captured my attention. To get things done, to get things to work, fascinated me.
In 1964 or 1965, I came across an interesting article in one of these Popular Science magazines, and in the show-and-tell presentation I talked about, would you believe, the continuous-wave ruby laser. I think that was one of the talks that was certainly above the level of my fellow students. It was just two or three years after the CW ruby laser had been invented. And it was so fascinating to learn about this new sort of light. The first time I learned about population inversion. Way later at Bell Labs I got hold of those man-made ruby bars from the 1960s, which are now a treasure in the desk drawer.
The only thing that my fellow students walked away with was that there’s a new abbreviation, L-A-S-E-R, light amplification by stimulated emission of radiation. It was fun to learn about new high-tech topics that no one around us had actually heard about before.
In the Austrian system, do you declare an academic focus at the outset for university, or that comes later?
In general, yes, you enroll in a department. As I went to ETH Zürich in Switzerland it was the Department of Mathematics and Physics.
Perhaps a few episodes from my pre-university times are worth mentioning.
At high school level, we did not have any particular advanced placement courses. Whoever went into theology or into physics, we all had the same kind of education until age 18. The only way to get to do what I liked to do was to do everything outside school. So I had hobbies. We were building model airplanes, not from sets to stick together, but we just got the plans. I had to translate it onto the wooden planks, cut them out very, very carefully, assemble and glue them together, and balancing everything. At that time, it was in my early teens, I learned to use my hands very, very precisely. I learned those kinds of skills. We also had RF-controlled airplanes. Some were sailplanes, with wingspan up to of six, seven feet. Wonderful gliders. Others were motor powered airplanes that were lots of fun to fly, of course. That was one of the hobbies.
Then later on, with the same friend, we went into rocket building. Now, why was that? The answer is NASA. In the mid-1960s NASA did a road show across Europe. It was on a Sunday morning when NASA came into our little town, with all the models of the rockets at that time, topped by Saturn V. It was the beginning of a big, big era. And we were so fascinated by this development, we thought we want to build rockets, instead of airplanes.
Now, the rocket itself is rather easy to build if you know how to build model airplanes. But we could not buy rocket fuel, we had to make our own propellant. And that story, as you can imagine, made a very decisive point in my career. Because there are two aspects. First of all, the chamber where the fuel goes in, has to be very strong. We came up with the idea to use the carbon dioxide cartridges that are used in the soda machines. When they are emptied, they were perfect containers for the fuel, including a nozzle. So this first step was our invention, so to speak.
Step two. What goes into the cartridges was based on a rather well-known recipe, based on what is called a herbicide. It was a sodium chlorate, which is an extremely oxidative white powder. And if you mix it, for instance, with sugar, or worse, with activated charcoal, you have a very good propellant. So, our rockets took off very well. And I always was trying to improve the propellant, until it was so good that it self-ignited in our basement.
The whole thing exploded, and I was so lucky that I had my hands above the cartridge, otherwise I would have lost fingers. No question. The only damage [laugh] that I had was a big splinter of steel in my belly. It’s still there, and later on was once misinterpreted on an X-ray picture as a large kidney stone. Lots of blood, and hearing problems for a few weeks, but I was quite lucky. The neighbors came to look at what had happened in our house. So at that point I realized, “Physics is more controlled than chemistry” and I gave up the option of studying chemistry. Allow me sequel to this episode.
Jumping ahead some ten-plus years, at Bell Labs, I met a friend who at the same time, about 500 kilometers away in Frankfurt, Germany, did exactly the same rocket experiments, had exactly the same idea with these cartridges, and it also ended up with an explosion. But he was less lucky, as his fingers got badly damaged.
And you know this gentleman. Horst Störmer.
Oh, wow! That’s amazing! That’s amazing! [laugh]
One evening over a glass of wine Horst and I exchanged those stories of our youth. And we could not believe how similar they are. And each one thought he was very original. [laugh]
That’s amazing. [laugh]
I also found it amazing! We are still laughing about it. Anyway, so that was part of the outside curriculum.
Bertram, why ETH Zürich for your education? Why did you choose to go there?
Originally, I meant to go to University of Vienna or to University of Graz, which are both good universities. So my mind was set. Then in between came this one important year with consequential decisions. In Austria we had compulsory military service, so for one year, I was off any academic activities.
And two things happened in that year that brought me to ETH. The first one was at the military service, where I was with the high-mountain troops. The field exercises were quite harsh. In one particularly grueling exercise, we were snowed in for a few days in these small snow caverns that we had dug out. Supply lines collapsed, essentially, we barely had enough food. We did survive, with some frozen toes. But we didn't get enough to drink for quite a few days as we had to melt the snow ourselves, which is a pain in the neck to do. And that hurt my kidneys.
Back in the barracks, I had enormous pains and the military doctor very badly misdiagnosed the cause. On the weekend I went to the private doctor at home, and he diagnosed right away a serious kidney stone as the reason for the pain. You might have heard about renal colics. Our mom told us that renal colics are more painful than giving birth, and she knew what she was talking about.
So the doctor did not allow me to go back to the military, I had to stay home for about three weeks, drinking lots and lots and lots and lots of a particular tea, until the stone had passed, which was wonderful. But in these three weeks, I had all the time at my hand, and could meet with this particular nice young girl whom I had known from mountaineering the years before. We became good friends, and half a century later we are still a happy couple. The incompetence and missing mastery of his craft by the military doctor had a very positive consequence in this case.
The second decisive event was that a friend of mine, one year senior, had started his engineering studies at ETH Zürich, and he told me how much he liked ETH. Zürich is only about 100 miles from home, while Vienna is some 400 miles away. ETH had already a very good reputation at that time, and by now it is one of the highest ranked—I think it is the highest ranked university on mainland Europe.
So, I took this invitation and applied to ETH Zürich. ETH Zürich is a Swiss public school. I had to apply there, but was admitted without exam, actually, because of the high standing of our gymnasium and because of my grades. We had paid almost no tuition—a few hundred Swiss Francs only. And because the cost of living was so much higher in Switzerland than it was in Austria, I even got a stipend and tuition waiver from ETH. They treated me so well. So that’s why I went to ETH Zürich. Again, influenced by friends. Opportunities open up, and you have to make a decision, and sometimes it is the right decision. Obviously to go to ETH made all the difference in my life.
Bertram, being an undergraduate in the late 1960s and early 1970s, were there any campus protests at ETH Zürich?
Yes, even in tranquil Switzerland, [laugh] there were protests on the streets. Yes, of course! But technical university students usually are not as adamant as philosophers, sociologists or historians are. But yes, students went on the street and were demanding reforms. And those reforms did happen. And as a student representative, I was involved in negotiating these reforms. Yes, we did make changes, and faculty members were quite open minded, and the reforms worked out pretty well. So I do have good memories of those years. Yes, it was the 1968 movement that even came over to Switzerland a little bit.
Were you political at all? Did you take part?
Well, I took part but not in a partisan way, but I was involved as a representative of the students. I was involved in getting together with the professors and trying to find a way to better organize our department. Our student organization, at some point even managed to get a lecturer replaced in a particular class, because the present one just was not a good teacher. He might have been a good scientist, but he was such a lousy teacher that we students protested so much that we got a replacement. So yes, as a student I had an open mind for teaching and its organization. And some 20 or 30 years later, as a director of studies on the other side of the aisle, I was equally open to the students’ desires and concerns, and I still am.
Bertram, what kind of physics was emphasized as an undergraduate? What were you exposed to? What seemed to be most promising at that point?
Well, in the first semester, we only had mathematics, no physics at all. Then came introductory physics taught by Werner Känzig, who was a fantastic teacher. He handed out a wonderful handwritten manuscript that he reiterated every year, literally cut and paste at that time, by hand. And he was an enthusiastic and very energetic person. We liked him, and he made a big, big difference.
He was an efficiency-oriented person. Actually, he came from General Electric Research in Schenectady, New York, where he had spent some years and then came back to ETH. So he had experienced professional life in a different place and different, efficient corporate culture. He didn't like administrative nonsense. When he passed away, a rubber stamp was found in his desk drawer that said “Professor Känzig has no time to fill out questionnaires.”
Very often later in my life I wished I had a stamp like this.
[laugh] That’s great! Bertram, what exposure did you have to laboratories and experiments as an undergraduate?
Well, yes, that’s the point. We also had introductory courses in solid state physics by Georg Busch. Busch from Zürich, not Bush from Texas. He had founded the solid state physics lab and he also was very good in setting up the laboratory courses for students, exposure to doing experiments. We were trained for years and years to do these experiments. While the experiments were sort of preset, we sort of knew the answer, but you just had to go through the routines, including estimating the errors. Thus, Busch’s introductory solid state physics lectures and these laboratory courses had the biggest influence on me.
In some sense, Busch also became my academic grandfather because he was interested in semiconductors, in ferroelectrics, and in magnetism. And so he set up a broad Rare Earth magnetism research at ETH. And as you know, Rare Earth physics and my early research topics intermediate valence and heavy fermions are very closely related. And as a side remark, perhaps of interest to later readers, I may add that Georg Busch and Bernd Matthias—you have heard his name from Zachary Fisk and other colleagues, perhaps—
And the award for which you were recognized.
Yes, exactly. So Matthias and Busch both were assistants with Paul Scherrer, one of the forefathers of condensed matter physics. Busch stayed at ETH, and Bernd Matthias went to the United States, first to MIT, and so on and so on. So I didn't know at that time how closely I was connected to Bernd Matthias. Later at Bell Labs I met him in person.
Oh, so you asked about the other experience as undergraduate. Of course, the laboratory courses were one thing. And then my later thesis advisor, Peter Wachter had a big influence on what I did, in the sense that he gave me all the freedom and support to do what I wanted to do, even during my diploma thesis, somewhat similar to an extended master’s thesis. And I always knew what I wanted to do. We had long, long, long discussions and heated debates about the next steps almost every evening before he went home for dinner. The other students thought it was impolite, but we had very good exchanges, and he’d give me all of the freedom to do what I wanted to do, which was also very good for my later PhD work, because it allowed me to do crazy stuff that came to my mind. Yes, that was a very important aspect of education.
Finally, I mention Hans-Christoph Siegmann. He was a young professor as well and was a pioneer and the inventor of spin polarized photoelectron spectroscopy of solids. He gave excellent conceptual courses of condensed matter physics in general. So the exposure to solid state physics was broad and rich. On the other hand, nuclear or high-energy particle physics did not have the same appeal, because I did not know how to do that physics with my own hands. I knew how to measure electrical transport or magnetic properties, or how to build cryostates or high-pressure cells, with steel or with diamonds. But I just could not imagine being part of a multi-hundred-person team, not even seeing what you measure. So my hands-on experience as a young man inevitably brought me to table-top condensed matter physics.
And it was condensed matter at that point? That’s the term of art?
No, no, sorry. It was solid state physics, actually Festkörperphysik. I don’t know how your German is, but it means hard bodies, solid bodies. [laugh]
But that accords to solid state, as you understand it.
It is solid state physics, yes.
Bertram, culturally, was the expectation for top students to stay on at ETH, or to go elsewhere for graduate school?
Well, the system was different. It has only slightly changed now. We had what is called diploma track studies. Usually after four and a half, five years, you would end with a diploma. And then later on a few students continued with the doctoral studies, almost exclusively at ETH. While working towards the doctoral degree, we were not students in the usual sense, with classes and exams, no, we were scientific collaborators, because we were part of a research group, of our choice. And we were for at least one day per week involved in teaching. What were at that time diploma studies later on were reorganized into Bachelor and Master programs, following the Anglo-Saxon scheme.
So, was it usual to go on? No, not too many students in physics stayed on to do a doctorate. More so in chemistry. And almost none in mechanical engineering. A doctoral degree in engineering was not very popular. Wasn’t necessary, because an engineer has to get stuff done, has to know how to do things. In physics, it’s somewhat different. So I did stay on, and I had a hell of a good time, as a doctoral student. I got all the freedom and support.
Did you know who your graduate advisor was going to be, even before you started graduate school?
A word of clarification. Well, as suggested before, there was no formal graduate school. When we worked towards the doctorate, we only had to take one or two courses, no exams. The only activities were, doing research and being a teaching assistant. That’s why we got paid. We got paid quite reasonably, actually. My starting salary at Bell Labs was only half my final salary at ETH Zurich. So graduate school in the sense of a school and a curriculum, did not exist, at all. We were completely focused on getting our research done, essentially. We took courses on the side, our own choices, which I did a lot. I enjoyed them. But there is no school. Which is a big contrast to what is known in the Anglo-Saxon world, of course.
So when is the transition? When do you start formally doing your research thesis?
Exactly. It’s what you had asked, David. In order to get the diploma, you have to do a diploma work, which is comparable to a master thesis. So I did the master thesis in Peter Wachter’s group and he offered me to stay on for a doctoral thesis. And I just continued without a break.
And what was that group doing? What was the research at that point?
In the broadest sense, it was rare earth compounds, rare earth magnetism, and optical spectroscopy to study the electronic structure. And they also had lots of experience. in growing crystals. Emanuel Kaldis was an excellent crystal grower. So we could produce all the materials that we wanted for our physics experiments. And that was an important part of being internationally competitive.
At the very same time, just about a year or so before I started my diploma thesis, an important paper came out of Bell Labs by A. Jayaraman, Ernst Bucher and colleagues. Both became good friends, later, and I’m still in contact with them now. They reported the discovery of a pressure-induced semiconductor - to - metal transition in Samarium sulfide, SmS. A landmark discovery. The necessary pressure is quite modest, six and a half kilobars. You can produce it just by using the tip of a needle to scratch the surface of the SmS crystal. The scratching permanently transforms the black crystal to a metallic golden trace. It’s a spectacular experiment to do.
For my master’s thesis, my task was to figure out the mechanism, and what drives it. I figured it out pretty well, and I published a paper in Physics Letters. Physics Letters had the high reputation then, because important papers were published there by high-energy physicists, and also by e.g., Brian Josephson. Anyway, I published this paper and then continued to work on intermediate valence 4f compounds. Because this golden high pressure SmS is not the usual metal. Samarium is in a mixed-valent state. The electronic configuration of Samarium is a quantum mechanical superposition of divalent 4f6 and trivalent 4f5-5d1. The one electron in the d state forms the delocalized metallic state. Nowadays, one would call it a novel quantum material. We just knew it was a quantum mechanical mixture. That was in some sense the main direction of my research. There were several other related and interesting compounds later on in my doctoral thesis.
But the one point I want to mention is that systematically reading the literature stimulated many new ideas. I knew what the colleagues at Bell Labs were working on at that time. Bell Labs, —this special place, we only knew from papers. And we also knew what colleagues at IBM Yorktown Heights were doing in this field. During my doctoral thesis I had essentially two big competitor groups at those places.
I think I did reasonably well in the competition, and by the end of my PhD, I had published, I guess, more than a dozen papers, including one PRL where, together with my colleague Hans Ott, we had confirmed in Thulium selenide TmSe one of the predictions that Chandra Varma at Bell Labs had made. And no wonder I had an opportunity later on to join either one of the groups, from being a competitor to being a collaborator.
I'll direct my broad question earlier specific to this point in your career, when you're really starting to develop your professional identity, and that is the interplay between theory and experiment on this research that you were involved with right at the moment between graduate school and your professional career.
Well, it was not textbook stuff.
Because it was all new, you mean?
It was new. It was at the forefront of what was going on, in the best of minds in the world. And we were at this remote place, somewhere in Europe, in Zurich. But the driving forces were in the United States, in the two laboratories mentioned before, I was closely watching what was going on there. Typical for the generous support I enjoyed—I think it was in the second year of my doctoral thesis—Peter Wachter sent me to a magnetism conference in Toronto to present a paper. As a young kid, well before the doctoral thesis was done. And at that occasion, I also traveled to Murray Hill to meet these famous people that I had only known from papers. And I got to know them all. And from then on, I could connect faces to all the theories and experimental results that came from Murray Hill.
On the same trip, if I remember correctly, I also had visited IBM. I met Fred Holtzberg there, and Stephan von Molnár, who passed away last year, and Tom Penny. I was a very, very young scientist working on the same topics. And I found it enormously stimulating to have this exposure to the world, to the leading people in the world, while I was still working on my PhD. Some twenty, thirty years later back at ETH, students in my own research group were encouraged to attend conferences, including the APS March Meetings. Students need to know what the world looks like in science. It is not the papers, only; it’s the people, and how they think. Leading edge theoretical concepts I got through personal contacts, not so much through papers, and certainly not from books.
How was your English before you got to the United States?
Horrible! I didn't have any English in Gymnasium.
Yes! Because, as I mentioned before, our part of Austria was occupied by the French troops. So I had eight years of French in school!
[laugh] You could have gone to Saclay.
Perhaps I could have gone to Saclay. I don’t know! No, there’s a big difference—if you come to the United States with an accent, which I never could get rid of, and you speak decent English, people are so friendly and say, “Oh, I like your accent. It’s so cute.” That’s our experience in the United States. If you go to France with a school French, which was pretty good, but of course not with a polished pronunciation, I always felt as a stranger. The attitude towards a foreign person speaking your language in France is different from what it is in the United States. It’s just a cultural observation that we have made, which made us, my wife and me, feel very welcome in the United States. Because people were taking us just the way we were.
Yes, I had one year of English classes in the evenings at Zürich. And when I gave my first talk at Bell Labs, the English was rather bumpy, but it worked out okay at the end. But I must add that later on, I had a wonderful secretary at Bell Labs, and she was English teacher. Jeannie Moskowitz corrected my written English so well that in later years I could correct my peers’ papers, even when American English was their mother tongue. [laugh]
Bertram, did you understand—among Americans who were graduating at this point in your field, everybody well understood that Bell was the center of the universe. It was the place to be. Did you have that understanding as well? Did you come to Bell with that appreciation?
Yes, I did come to Bell Labs knowing that this was the Mecca. Also because it was just the year before that Arno Penzias and Bob Wilson got the Nobel Prize, and the previous year it was Phil Anderson’s turn. So even that was so obvious. When I walked in this building the first time, I met these people that I only knew from these famous papers. There were so many respected theorists around, Phil Anderson, Bill Brinkman, Maurice Rice, Chandra Varma, Jim Phillips, Pierre Hohenberg and many, many others. I'm sorry if I can’t mention them all.
Not just theorists; the number of world-leading experimentalists there was mind boggling as well. Some of my early lab neighbors were Doug Osheroff, Mikko Paalanen, Denis McWhan, Jerry Dolan, Dave Bishop, Gordon Thomas, A. Jayaraman, Klaus Andres, and Horst Störmer, of course. And you realize immediately that each one of them was a top expert in at least in one field, in a technique. In addition of being very smart people, I saw these experimentalists also as enormously skilled craftspeople, if I express it correctly. Mastering the craft in experimental physics is an important ingredient. There are many smart experimental physicists, but there are not as many outstanding craftspeople in experimental physics, who make new developments happen, design new experiments, come up with ideas how to perform novel measurements.
And I always measured myself on that level, trying to be also a craftsperson. After all, as a boy, I much liked hands-on work. So yes, Bell Labs was an assembly of theorists and experimentalists of the highest caliber, interacting with each other, which was an enormous challenge for us young people joining the Labs. It was stimulating but not intimidating, I would say.
And you skipped the postdoc step? You went right to technical staff member?
[laugh] Almost. Almost. They hired me as a postdoc because of the visa situation. [laugh] And then one evening —it was perhaps half a year or so into my first year—my department head, John Rowell, came to the lab and asked “Bertram, would you like to stay a little longer?” And I said, “Oh, John, I don’t know. I have to ask my family.” So this was the lowest key job offer I ever got. [laugh] It was totally low key, typical for John. “Well, if you’d like to stay on, stay on.” And that was it. I talked with my wife, and she said, “Okay, let’s do another year or two perhaps. Not more than that. Then we'll go back to Europe.” And as the saying goes, “I never finished a paper at the end of the year, so I had to stay yet one more.” [laugh]
What group did you join when you got to Bell? What was your first project?
It was a continuation of something which I did at the very end of my PhD, when Jim Allen from the United States visited us. He brought a small piece—a very, very, very, small crystal of samarium hexaboride, SmB6. Nowadays, everybody knows this material. It was known to the mixed valence people at that time, and some ten years earlier Ted Geballe and colleagues had worked on that compound, after a group in Russia had earlier discovered it. I is also a mixed valence situation in some sense, but the electrical resistance just shot up at low temperatures, rather than dropping as in a metal. So the question was, is this a loss of mobility, or is the number of charge carriers decreasing?
So Jim Allen brought this crystal, and again my craftsmanship was challenged. Five leads had to be attached to this crystal. We could not evaporate contacts. So I had come up with a holder with five spring contacts that were pushing on the tiny crystal for Hall effect measurements. And then we did Hall effect measurements and found the resistance increase at low temperature to be caused by a loss of carriers. So there was a gap in the density of electronics state at the Fermi level. It was a small-gap semiconductor. Nowadays, this paper is cited again frequently. It turned out to be a Kondo insulator. Today we know much more, also in the context of topological surface states.
Coming to Bell Labs I thought, “I would like to measure the gap spectroscopically”. It must be very small, some milli electronvolts. I asked John if I could do a tunneling experiment with him. John Rowell is the world expert in superconducting tunneling spectroscopy. And he agreed. First, we had to grow single crystals. With Paul Schmidt we grew single crystals out of aluminum flux, and then and I did these tunneling experiments in John lab, following all his recipes and advise. Hurrah, the gap was there, indeed. But there was a hitch.
If you have a good junction in a superconductor, the conductivity at zero bias voltage goes to zero, and goes up when the gap energy is reached. But in my junctions, there was always a little bit of conduction at zero bias. This disqualified these junctions completely in the eyes of John Rowell or Bob Dynes, who are the world experts in tunneling and said, “Your junctions are just leaky and crappy, because you don’t have zero conductance at zero bias.”
Well, I was not an expert and took their word for it. And we published these results only as a conference proceeding, never as a paper. Much, much later on, these identical types of measurement with zero bias conductance were taken as proof that there is actually a topological surface state on this Kondo insulator. So I had measured this topological surface state way back in 1980 or 81, except the results were not understood or misinterpreted, but not recognized as the breakthrough. So much about my first experiment at Bell Labs. Just check it off and leave it to the history.
What was the research culture like at Bell when you arrived? In other words, was it collaborative? Was it informal? Can you bump into people and exchange ideas? Or was it more regimented than that?
In the physics area, it was not at all regimented. Collaborations were encouraged, and actually it was even better if you could collaborate with someone outside of your organization, because then the sum of the credit at the end of the year performance review wasn’t 100%, it was 150%. Among the experimentalists, the question was “Is the person doing something interesting? And is she or he doing it well?” We didn't have many ladies there.
The most important thing about the culture I found initially was the fact that at lunchtime we're sitting around round tables, mixed up from different departments, different areas. And everybody would tell the latest from the labs. Imagine this. So we got to hear and learn so much about the ongoing research in completely different areas, educating each other about what was hot. Not what was in the newspapers or journals, because we worked on the hot problems. Another gathering was for afternoon tea at around 4:00, when physics area people came together and had this awful-tasting Lipton’s tea. Just a huge aluminum kettle with hot water, and sort of tea, and the cheapest cookies you could buy at the grocery store.
But it was the most important social activity, again, to talk about physics. There was only one time in the year when you would not talk about the physics, in early April, because April 15th, was an important deadline to submit the tax returns.
Anyway, this open culture was fantastic. And there also was the tradition of open office doors. The lab doors had to be closed automatically because of safety concerns, but the doors in the hallways to the offices were all open. One could hear, just by osmosis, what was going on. Sometimes it was a little embarrassing to hear my fellow theorist, whose name remains unmentioned, fighting for an hour with Gene Wells at Phys Rev Letters about his rejected manuscript. It was also part of the lecture for a young scientist, what was going on. One could just walk in and ask anybody about physics.
Perhaps two more aspects that I remember about the culture. One was the journal club. Once a week or every other week, a few of the scientists were reporting about a result they had read in the journals. And it was always a very critical way of telling new physics to all of us. The level of scientific exchange there was amazing! People were really arguing science there. For us young members of staff, it was sometimes intimidating to experience the high level of scientific exchange. But the good lecture about it was, as much as they were fighting in the morning, in the same evening, we might have a party at somebody’s home, and the same people would have the best of times together again. This separation of professional disagreement and personal friendship is something which was so new and unique for me coming to the United States. I really enjoyed it, as it also contributed to the bonding.
Quickly one last example of the special culture. Particularly beneficial for both sides was the constant exchange with theorists. Chandra would ask me what I had measured today, and this often led to long discussions. I would be guided by his insight and experience, and he had firsthand access to the latest results, stimulating also his thinking.
What was your next project? What did you take on next at Bell?
Oh, gosh. I always had many things going on at the same time, including superconductivity, heavy Fermions, and a few other topics. I remember [laugh] cuprous chloride, CuCl - because it got me into superconductivity. A paper in a Russian journal reported that if you squeeze on CuCl and cool it down, you would see resistance drops and jumps that were indicative of superconductivity at enormously high temperatures. And a colleague in the United States also reported having observed resistance drops. Speculations about excitonic superconductivity started. And I thought, this is just crazy. Cuprous chloride, as I remembered, is just a transparent insulator.
And so I got together with Joe Remaika in our department. You might have heard Joe’s name before, from Zachary Fisk. Joe was a self-taught amazingly creative wonderful person, growing crystals of all kind, and a good friend and mentor who passed on way too young. “Joe, can you make cuprous chloride, CuCl?” I asked. And he came up with a fantastically simple and efficient method to make the world’s best CuCl crystals. So I got these large, centimeter size crystals, which I had to cut because they did not fit in the equipment. I did various kinds of high pressure experiments on them, and there was no trace whatsoever of superconductivity there.
What I did find out is that under pressure, cuprous chloride could break up into CuCl2 and copper. Copper was segregating into metallic filaments, perhaps, and these filaments probably were the reason why the resistance drops had been seen before. High pressure induces crystallographic phase transitions, and I also found ionic conductivity, but all of this was just a sideshow. Cuprous chloride is no superconductor whatsoever.
To complete the story with an anecdote. At the March meeting, the speaker before me warned, “Oh, one has to be so careful about this cuprous chloride. It is hydroscopic, and you have to treat it carefully.” When my time came, I reached into the pocket and put this centimeter-sized piece of colorless cuprous chloride with bare fingers on the overhead projector, and said, “Cuprous chloride is not air sensitive at all, and it is very stable.” That was the end of the discussion, actually. [laughs] Joe’s expert craftsmanship was essential for solving the puzzle. This was the only Physical Review Letters that I remember reporting a negative result.
What’s the significance of that?
Cuprous chloride does not host excitonic superconductivity, was the message to the community. For me personally it was the first encounter with unconventional “superconductivity”, even in a non-superconductor. Then I started a few other projects, including, the pressure-induced compressibility collapse transition in ReO3, and heavy Fermion magnetism and superconductivity, mainly with Zachary, Jim Smith and Ernst Bucher as crystal growers, and local collaboration with Davis Bishop and Brage Golding. Quite helpful for my later science was work, again with Joe, on barium lead bismuth oxide, Ba(Pb.Bi)O3 , that Art Sleight had found in 1975 to be superconducting at around 12-13 Kelvin. The novelty was oxide superconductivity with a Tc above ten degrees, and it gave me quite a head start.
At that time, colleagues in Japan around Koichi Kitazawa and Shoji Tanaka, had also been working on this oxide superconductor. So I had known these people from the pre copper oxide superconductivity days. And we became good friends later on. That was the beginning of my sliding into superconductivity. I never looked at an ordinary superconductor, just materials off the beaten track.
Bertram, what were some of your key responsibilities as head of the solid state physics and materials research division at Bell?
To do good science.
So you did not see it as an administrative role, primarily?
Not primarily. The circumstances had been very peculiar there. It was in 1986, our department head left for a university position. Back in Austria for a family summer vacation with our parents, I got a phone call from our director, Paul Fleury and he said, “Bertram, can you return next week to Bell Labs? I want to introduce you to your department as the new department head.” So much about direct management style.
No formal interviews. Just, “Please come next week. You are the new department head.” Period. [laugh] Yeah, so I had to cut my vacation short, to show up at this particular meeting with our department. I think I was among the youngest staff being a department head at Bell Labs. The timing was peculiar, it was August 1986, and a few months later, high-temperature superconductivity broke. There was not much time for administration, other than performance review at the end of the year. I had to do physics in the lab, day and night. So I was excused from many administrative duties that otherwise I would have done as a department head. Later on it changed, of course.
The point was always to make sure that good science is being done, and properly published, and that research would go in the right direction. But it was not a top-down decision making. The goal was to keep administrative burden away from the members in the department. The main charge that I felt, was to let them be good scientists with proper support. So that was my role. And then, an important part was the performance review at the end of the year, which is a chapter that we might talk about separately. It was a big administrative and also a daunting job, however it was also highly rewarding. We learned so much about all the physics that’s going on in the entire laboratory. So yes, there were administrative chores to do, but at the beginning high-Tc was very high on the priority list.
Bertram, I'm curious, in the program review, I wonder from your vantage point, what was your sense of the balance of priorities at Bell Labs between basic science and research that was actually valuable to Bell as a corporation for its bottom line, for its profits?
Significant differences between the mid-1980s and the late 1990s. Well, that part was not even a question at the beginning. And as you might have heard from other people, the bottom line became a key question towards the end of the 1990s when the company’s structure was changed drastically. “What do you do to the bottom line?” had a clear answer, because it was understood that in the long run, research output would end up benefiting this fully integrated company. Manufacturing and services were in one company. And this was the base of having this wonderful research organization at Bell Labs.
Our physics and the bottom line: when NCR was a subsidiary of AT&T in the first half of the 1990s, our department had a rather productive and successful collaboration with the NCR developers in Atlanta. Gordon Thomas with the help of data base experts in the mathematics division, developed an optical spectroscopy based system to recognize fruits and vegetables at the check-out counter. Several prototypes were tested in stores with satisfactory results. An example of optical spectroscopy trying to help the bottom line.
As a German speaking physicist, I got asked several times to participate in sales-related meetings at highest corporate levels in Germany. Our NCR colleagues wanted to impress their customers with Bell Labs’ broad expertise, which I then was asked to represent. The board room meeting in the Springer Verlag building was such a memorable occasion, or a “business dinner” in Nürnberg over Bier and Sauerbraten…a long way from superconductivity to the “corporate bottom line”.
Was it the discovery of high-Tc that prompted your collaborations initially with Bob Cava, or had you worked with him before 1987?
Bob and I knew each other from the hallways, we were good colleagues, but we did not collaborate. [laughs] I think once I bought a used record player from him, when we joined Bell Labs, but that was the only business transaction that we might have had before. High Tc brought us together. And it was a particular seminar that we attended when our colleague Kitazawa from Japan reported about the first copper oxide superconductor. Immediately we got together and struck up a wonderful collaboration for many, many years, and a lasting friendship. We have a very similar attitude towards tackling a problem, and we have complementary expertise. He is chemist, materials scientist, ceramist. In the end, we cared about and tried to manipulate what the electrons are doing in a crystal. And so we said, “Look, electrons do not care how the physicist or the chemist talks about them. They do know themselves exactly what they want to.”
And so Bob and I always found a common language to proceed, to exchange ideas, and to stimulate the next steps to be taken. And so it was more than a materials preparation person on one side, and a physicist measuring it on the other side. All was based on sitting together and exchanging ideas.
Bertram, as with every formative scientific collaboration, I'm always curious about, as a matter of intellect, or intuition, or personality, what did you bring, and what did Bob bring, to this joint research that you conducted?
Is this a performance review question?
[laugh] That’s great!
[laugh] Having previously worked with mixed valence and with heavy Fermion compounds I had a good understanding of how to use the periodic table to manipulate electronic properties. Substitutions, changing stoichiometry, or varying the ionic radius are powerful tools to manipulate the electronic part. And Bob understood very well that if you replace lanthanum and barium and whatever you come up with would influence the preparation parameters required to obtain phase pure material, and what it would do to the structure.
This goal to manipulate the background and the ingredients in a favorable way, I think we both had in common. He knew how to make the compounds very well, and to analyze the structure quickly. And I brought to the table how to measure it, how to make sure we knew what we had in terms of physical properties. So it was a collaboration on the same level, towards the same goal, but we had different parts of the task separated for us.
What were some of your main findings in your research with Bob? What was so significant?
The identification of single-phase yttrium barium copper oxide 1-2-3 YBCO, with superconductivity at 90 degrees, was a big hit. We wrote a paper and also reported first electronic properties, such as critical fields, temperature dependent resistivity, and the unusually low density of electronic states at the Fermi level. Before that was first La,Sr cuprate with Tc near forty K . But in terms of finding new compounds, we discovered several more superconductors together.
YBCO of course put us on the map. Very clearly. At the famous “Woodstock of Physics” March meeting in 1987 I presented all our work, and that of our Bell Labs collaborators as well. The single phase YBCO work and the following subsequent work, were the most important parts of our contributions at the very beginning. Later on, (Ba,K)BiO3, a non-copper oxide superconductor at 30 K, and several more studies of new compounds we did together. But there are so many papers, I don’t want to go through them in detail.
A few months after the YBCO single phase identification and physical measurements that were clearly hinting at non-phonon mediated superconductivity, new surprising insights developed. We were among the first to systematically vary the electron count by varying the La/Sr ratio or the oxygen content in YBCO. A general phase diagram emerged and over the years we explored it in more detail together with Art Ramirez, Hide Takagi and Harold Hwang. Identifying these phases involving spin and charge degrees of freedom became for decades a central theme in this research field worldwide.
Let me mention something about this YBCO 123 identification. Bob had told you before that we did it within a few days. It was a day and night work, and we had it, I think, on the third of March 1987. We sat together with the patent lawyer George Indig to write a patent. Now, this is yet another example that I would like to bring up, of incredible unique level of craftsmanship on the lawyer’s part. I hope I don’t abuse the word “craftsmanship” too often, but it is craftsmanship on the level that was unheard of.
So we had told George that we would come the next day with what we had found, and we would bring some data and so on. Now, imagine the following. Bruce van Dover, the other collaborator, Bob and I—came early in the morning, gave George some background information, what we had done, showed our data, and so on. In between we went back to the labs, got the latest data to make sure that we had everything together. And George would sit with his legs on the table, with secretaries on the left and on the right hand taking notes, and he would dictate the patent word for word. Barely a correction was necessary. And every 15 minutes, the two ladies would change, go back and type up what he had been dictating.
Because, as you can imagine, a patent is a very well-organized piece of document in lawyer-language, George had pre-structured it fully in his mind. It’s a different way of communication, not a scientific publication. It was foreign to us. And George did it the whole day long, taking our latest results and figures into consideration. The graphs that went into the patent, we gave to the drafts people during the day. And in the evening—I think it was around 8:00 or 9:00, the patent was completed, typed up, with all the graphs. The same day! In all the coming years, this document and its content had withstood the harshest of interrogation and cross-examinations. And why it then took more than 16 years, allegedly the longest ever, for the patent to be granted in 2003, is known to a few people only. A story to be told separately.
An absolute key patent was produced in one day. And it was sent off with a courier to New York in the evening, and that was it. We went to write our paper the same night, the Phys Rev Letter, with more recent data measured during the day, and it was done in the morning. So this PRL was written in one night as well!
It was a long night, but it was a good night. My wife was wonderful to bring us coffee to the lab, and a freshly baked sheet of cornbread, if I remember correctly. So the next time we looked around, all coffee was gone, it was morning, and the paper was written. We left it to my secretary to type it up, and then it went out in the afternoon! At the same time, we sent out a large number of preprints by express mail, to all our colleagues in the world, so that they would know that we solved the problem of identifying the 90K superconductor. Well, all people involved, we still talk about these particular days. It was magnificent, to bring it all together, and have it done.
What was most intellectually satisfying in this moment for you?
It was that it was a new chapter in condensed matter physics, somehow. We had a single phase, a clean material, not a mixture of green and black stuff, not superconductivity that would occur at the interface or something like this. No, it was a solid piece of superconductor. And by the way, I still have half of the original disk that Bob made in the desk drawer. It did not deteriorate, it is stable. As a trained ceramist Bob knows how to do materials preparation. And at the same time, the first physical measurements strongly suggested the presence of unconventional superconductivity.
The stimulating part was that we had something in our hand that was the basis for further intense exploration. Yet we could not anticipate how intellectually challenging it would be to answer all the physics questions, as we discussed earlier in the interview.
Bertram, to go back to that Socratic problem, what were you so optimistic about understanding truly, but only in retrospect did you realize that you couldn't at the time because of how little you knew?
Well, in this context I think of another experiment, which I performed myself in my laboratory, the so-called isotope effect. At proper temperatures, and with a full control sample at the same conditions, I exchanged the usual oxygen-16 in the sample with the heavier and quite rare oxygen-18 isotope. Raman spectra showed the expected lowering of the phonon frequencies, but Tc remained essentially the same in this 90K material. This was a key result, strongly suggesting that it was not the conventional electron-phonon mechanism, and that we were entering conceptually new territory. So I think this isotope effect result was an incredible kick to our minds that, wow, it must be something really new. Not knowing what it was that was new, but it had to be something new.
And then much later, systematic studies across the phase diagram by other researchers revealed that this isotope effect gets very large far away from the optimal doping. Equally crazy in terms of not understanding it, even in the context of what we now know. But so this was one of the key steps in realizing that we had a gold nugget in our hands.
Given the significance of the discovery, how did this change both Bell Labs itself and the field more broadly, immediately? What were the immediate changes that were felt as a result?
Well, we could not contain our optimism, I would say. We thought that this would make such a big difference in terms of how we do technology in a broad sense. Of course, making wires and all of that. There was just this optimism that a new era had dawned, based on this new above-77-degree superconductivity. Occasionally, I was quoted—not quite in the spirit that I had intended, saying, “I think our lives have changed.” This was meant in terms of how our personal life had changed, working day and night. But it was taken as me trying to say that life of mankind has changed. Nevertheless, I'm always laughing when I see this quote somewhere in the public discourse.
But what had changed was that it became obvious that physics in the broad sense, and condensed matter physics in particular, had much to offer. There was not just silicon that brought all the changes. More would come that might be—we thought will be—beneficial to mankind. I think it was this idea that yes, cuprate superconductivity opened a new door into much more complex materials that will make a technological difference. Three and a half decades later, several applications in real life are emerging. And we also do know that the intellectual consequences of this discovery by Georg Bednorz and Alex Mueller, have stimulated immensely creative and fruitful developments in condensed matter physics in the broadest sense.
What did it feel like when you won the Bernd Matthias Prize, with Bob?
This was very nice. We felt much honored, and we were very humbled by it as well, particularly because I did know Bernd Matthias personally, and what he stood for, and we knew who got the prize before us. We were very happy, and we had an authentic Chinese dinner in Beijing, organized by local friends. Furthermore, the Prize also was a stimulant to keep on doing work of that quality and stick with the topic. As we both were awarded the Prize it was also our very special collaborative work style that was honored by our colleagues.
The following year, when you start to collaborate with Christian Kloc and Jan Hendrik Schön, how much were you working on the electronic properties of organic crystals up to that point? Or was this really a shift in research for you?
I would think it was curiosity, once again. It was curiosity. In the years before my focus had already been drifting to other themes, such as giant magnetoresistence and spin polarized transport in Manganese perovskites with Harold Hwang and Sang-Wook Cheong. Also, various transition metal oxides and other new classes of superconductors, including boro-carbides, were on the list, when we worked with Sue Carter. There were colleagues at Bell Labs, Ananth Dodabalapur and others, who were working on organic semiconductor devices. And I saw their papers, heard their talks, and I thought, “Well, that’s a very interesting different direction of asking what can electrons do in a material?” After all, these are transparent, colorful crystals.
But the point was, we did not have very good crystals. So I had asked Christian Kloc, who was working at Konstanz and working with Ernst Bucher, who actually was another one of my favorite people to collaborate with in the heavy Fermion field, together with Zach Fisk and Jim Smith who prepared the crystals. Christian came up with a simple and fantastic way to make super quality crystals of organic molecular materials. And this was sort of the starting point. I just wanted to have a good material. Not to be sidetracked by a dirty semiconductor. But I did not have personal experience in semiconductor-device research. I was obviously working in different fields.
That’s why we had asked Schön to join us, to do these kinds of experiments, because he did his PhD in classic semiconductor research. He was an expert and came with the highest recommendations. So I got in because I wondered how electrons can move in these crystals with strongly vibrating molecules. And that brings us to the very interesting intellectual challenge that still fascinates me today, because it is an example of what Phil Anderson actually wanted to understand and got Nobel Prize for. Transport of charge in a crystal that is not perfect. Not that these molecular crystals are dirty or disordered. They are perfect crystals except that the light molecules are moving with respect to each other, as they always have to do, quantum mechanically, even at T=0. And therefore, the very weak overlap of the electronic states is changing due to molecular motion.
In other terms, the problem is called intrinsic dynamic off-diagonal disorder in a perfect crystal. It’s a question of electron transport that was just not accessible for studies before. So much about the question that motivated our research, also when I came back to ETH and worked with outstanding doctoral researchers. So that is the intellectual background that I found stimulating at that time, and why I got into it.
And in terms of the collaboration, at what career stage was Christian and Jan, and when did you connect with them?
Christian and I are about the same age. We are colleagues and had collaborated before already. He did make some other materials for us when he was in Konstanz, and then he was invited to come to Bell Labs by Bob Laudise because Bob had been a crystal grower in his early years. He had developed the large-scale growth of quartz crystals for all kinds of large-scale technical applications. Christian came to Bell Labs as an expert addition to our staff. Schön had just completed his PhD. I myself was already looking for new directions and also possibly for new places to work. Put it this way, I was traveling a lot, had interviews on the West Coast and in Europe.
My presence in the lab was much reduced compared to what it used to be before. In 2000 I stepped down as a department head, also. That was towards the end, because I had announced that I would be leaving for ETH. You know why I mention this. The misconduct that happened was sometimes ascribed to a lack of supervision, which actually is not true at all. The point is that at Bell Labs, a postdoc or a young member of staff works independently. This is part of the culture that I should have mentioned before. When we joined Bell Labs as postdocs, we did not work for a particular person, nor did we work under that person. We worked as new young expert scientists, with enormous self-reliance. I did not work for John Rowell. I was allowed to use his laboratory and benefited from his expertise, I had my own ideas. And later as member of staff I did not work for a department head. Not at all. Our postdocs do not work for us at Bell Labs. They were always hired to bring in new, fresh expertise. That’s important to mention because postdocs in academia are usually seen in a different role. And when you asked before, what is the important part of a Bell Labs department head job, it’s to hire people that are better than yourself are. That was the unwritten rule, enhancing the quality through smart hires. That was a little bit of a side remark concerning cultural aspects at Bell Labs.
I'm sure you've asked yourself this a million times, but was there anything in your initial interactions with Jan that seemed off to you? Did you have any misgivings before there was anything specifically to be concerned about?
Not that I remember, no. He struck everybody as being a very friendly, a very kind personality. He appeared very considerate. And he made very good presentations, very good points. So the answer is no. Quite the contrary.
What about scientifically? Have you ever wondered why you didn't catch things or have concerns earlier than the point that this would have gotten to an investigation and a retraction of publications?
We had the usual discussions with Christian and with Hendrik. We had the usual discussions that we have among collaborators, sitting around the table or actually in the lab, usually, looking at data on the computer screen. These discussions went all just normal. Except that we knew that he was a very, very good experimentalist. That was the impression that we had, that we got already from his thesis advisor and his thesis work. So that was it. No suspicion. Actually, I remember Christian, who is a hobby photographer, taking pictures of working electro-luminescence devices under a microscope.
How should I put it? The misconduct happened independent of who the coauthors were. There were some 20 people who were coauthors. I was one of the better-known coauthors, but there were many—and there were numerous papers that I was not involved at all. Misconduct happened independent of the place where the various pieces of the experiments had been made. So some of the studies were done back in Konstanz, others at Murray Hill, in various labs. And also the misconduct was independent of who was department head or manager of the group. It was just not related to any of those factors.
And so when this came to light, the science community rightly was upset. All the coauthors were shocked. And I was more than shocked. I was shaken in my foundation as a person, as a human being, and I was shaken as a scientist. This was a traumatic experience for me, and I think I only made it through due to the help and support that I got from so many directions, including family and also friends in the physics community. It still works in me very frequently, actually. I had all this trust in a young person.
And perhaps that brings me back to what I had mentioned at the beginning, that I was brought up in a family where the goodness in people was kept very high. That we did trust each other. And for me, certain things in life were just not considerable. I think if I had grown up on the sidewalks of New York, rather than in this protected environment, I might have had a different predisposition towards meeting people in life. But for me, it was inconceivable. I did not even think of anything of that nature, it never crossed my mind.
Bertram, before we get to your understanding of the misconduct, we don’t have to talk of course about every single paper, but in sum, between 1998 and 2000, what was so exciting? What was the message in toto from all of these papers, about the nature of the research, about what was being discovered?
Well, there are several aspects, and I'm not sure if it’s a single one. The basic idea of field effect doping turned out to be particularly helpful. It originates, of course, in the functioning principle of the field-effect-transistor. Extending it to other materials and pushing it to the physical limits one can introduce enough extra charge to induce metallic states, and even superconductivity. All that without chemical substitutions. Either by using particularly good insulating layers, or so-called electric-double-layers. Numerous studies have employed this concept, and the latest example includes field-effect induced superconductivity in twisted graphene double or triple layers. A recent example of electron-electron interaction mediated superconductivity. That part might be seen as a valuable aspect of work reported in several papers tarnished and invalidated by misconduct.
When allegations of the misconduct first came out, did you feel more like an insider or an outsider? In other words, did you learn about this like everyone else, or was this something that you knew before others?
Well, I don’t remember all the details day by day, week by week. I would need to consult my notes. That’s almost 20 years back now. The fact is that I was at Zurich already for almost two years. So I was surprised to learn, in the whole process, that there had been investigations at Bell Labs that I had not been told about. I had not been alerted about the fact that there was the second investigation. Triggered by an outside request, I did ask about the first one at some point, but I was not kept very well informed, actually. The Bell Labs investigation did not turn out anything unusual, apparently, I was told at that time. Apparently, the presentation he made to these people was convincing. That’s all I can say. I wasn’t part of it, I was far away. However, when the official investigation started with Mac Beasley’s committee, then I was fully involved, of course.
Among all of the emotions that you felt at this time, what was most significant? Did you feel hurt? Did you feel betrayed? Were you upset? How might you have drawn on the lessons your parents taught you about being trustful of people?
Perhaps all of the above. However, I think being misled by someone who you trust was the most hurt. In addition, of course, the fact of observing the many reactions of the community with both polarities. I was surprised about some comments by colleagues that I thought would be more thoughtful in terms of first looking at the facts and then talking. Many people knew ahead of everything what was wrong. They were just so smart. And they were just wrong, as well. But that was hurtful as well. So there are many feelings that go with that, and still go with that. It’s not over yet. Perhaps I won’t enjoy dinner tonight, as a result of that. I hope not. But it’s something that shook me in my foundations. And, well, I don’t wish that anyone has to go through that, ever again. In addition to external reactions, a nagging concern was and still is, that I had presented some of the later discredited results in my own talks.
One can see something positive in that experience. I think we all have learned something from this disaster. As a community, we learned what can go wrong. And what has happened in the last 20 years in numerous other cases, was not much different. What we have learned is that being very critical, perhaps even a bit suspicious, appears to be necessary occasionally. That’s obvious.
As a result, a few years later ETH, I got involved in teaching two courses about scientific misconduct, together with a colleague who was doing science theory and philosophy. There was nobody who could talk more authentically about scientific misconduct, obviously. Students were very much appreciative of those discussions. Of course, a little bit of drama is involved here and there if you go through all the famous cases of misconduct, not just the one that we talked before. There are many such cases, well documented. They all make good stories, particularly if the lecture is at 5 pm in the evening. But I got involved in trying to spread the firsthand experiences to students, and also to some faculty, actually. At the end something positive could be made out of it.
Several times I was invited to scientific meetings to talk about this topic. Each time, it’s gut- wrenching. But I thought it was a good way for me to share experiences and share insights of what can happen. And at the end, I hoped we could prevent other things of that kind to happen again.
Bertram, what contact, if any, did you have directly with Mac Beasley, during this episode?
We had formal exchanges of documents, of course. And then I flew to Murray Hill and was interviewed, had exchanges with the gentlemen on the committee. I had known Mac before from the times in superconductivity. And I felt there was a high level of mutual respect, and I was very grateful that he took it upon himself to lead this very challenging investigation.
Of course, in your own heart, you would know that you did nothing wrong. But what concerns did you have about your reputation? About misunderstandings? About future prospects for collaboration? To what extent were you just concerned that your future in research was tainted by this?
It was not a concern; it was a fact. It was a fact. So I just continued to be a good teacher at ETH. Do my job there. And be a responsible group leader, as a professor with several doctoral researchers and technical staff. And we just did the best job that we could possibly do. And I was lying low, did not stick my head out for quite some time. For days I went to the lab, did measurements myself, mainly on Na-cobaltates, and just tried to keep levelheaded.
As you were trying to establish perspective—and again, to talk about some positives that might have come out of this—what did you learn about the importance of integrity in science that you may never have thought before, because you never even thought to think of it before?
As you put it correctly, integrity was not a point to be discussed. I took it as, if anything, as a given. I might call it naïve now, but integrity was not something at your disposal. It was just part of being, part of doing a job. When my grandfather, Mom’s dad, built wooden homes—he was a carpenter – it would have never occurred to him to take a shortcut, because the house would fall down 20 years later, to make the point clear. As a student in gymnasium one summer I had been working in a bakery. Well, bakers as craftspeople also know that you do not take shortcuts. You don’t sell 0.95 pounds of bread as a one pounder. So my experience as a young man working at various jobs was that there is no such thing as a shortcut, if you master a craft and want to be valued member of society. It has to be right and correct and trustworthy.
When I was a student at ETH, I had also jobs on the side. One spring break I was working for a company building hydroelectric turbines. These high-power, hundreds of megawatt hydroelectric power plants are fantastic pieces of engineering marvels. And around here in Swiss and Austrian Alps, you have these water reservoirs a thousand meters higher than the valley floor. A steel pipeline feeds the water to the turbine. And these pipelines have to be constructed with the proper wall thickness. You don’t have a factor of five reserves; you have to be correct within a few percent. And the person I worked with in the same department performed the necessary calculations. Here is the basic physics problem: of order hundred thousand tons of water move with the speed of about ten meter per second, towards the turbine.
Now if you close down the valve in front of the turbine, what happens to the kinetic energy? That’s comparable to the kinetic energy of the heaviest freight train in Europe running at full speed. Among other effects, a pressure surge is building up in this pipe. To calculate that properly is a challenging task, because of all the materials properties and the dynamic processes that need to be taken into account. So that person was calculating the pressure surges as a function of time and location in the pipe, when the valve closes at different speeds. And he had to be right within a few percent. He showed me his original calculations and compared them with the measurements, taken years later after the plant had been built. Right on! At that point I realized that solving differential equations is not just the fun of physicists; it is something that an engineer needs to have done to a few percent. Side remark: in those days the computer was programed by punch cards, in this case by a stack several feet tall. And for me, that was yet a new—another level of craftsmanship, of perfection. And I knew that he could not take any shortcuts. The whole company was relying on this one person doing a job right. His reputation was stellar.
Doing a job intentionally in a sloppy way, or even in a dishonest way, is something that never crossed my mind. Of course we make mistakes and things go wrong, but not in an intentional way. That was a quite long answer about what we have learned. Craftsmanship and trust are two very important ingredients, also in science.
Bertram, to be clear, your move to ETH Zurich was entirely disconnected from the brewing scandal back at Bell? You had gone before this had come out?
Well before. You don’t move into ETH overnight. I think in 1998 or so, we started talking about me moving there. This was years before the investigation in 2002. It was completely disconnected. Yes, I was way gone by that time. That’s also why I wasn’t collaborator and coauthor on many of the incriminated papers.
Did you have any desire to connect with Schön at some point, or did he ever reach out to you?
No. No. I wished not.
I'm hurt too much.
If he called and asked for forgiveness, would you give it to him?
We would talk for a while, and then I would see. Well, that’s a hypothetical question.
No, we didn't see each other at all, ever since. Had no contact whatsoever.
Do you believe in rehabilitation? If deep down inside there’s a good scientist there, and people are complex, and people make mistakes, is there room to resurrect a career? Or is this the kind of thing that says, “You're excluded for life”?
I don’t know. I'm not a psychologist. Of course, you use loaded vocabulary here. I know what the right answer should be, as well. I'm realistic. I don’t know what it would be. It’s a hypothetical question that did not come up. I had to work hard enough to make sure that I could get hold of my life and career.
Back to happier topics. So when you got to Zurich, and this was finally behind you, what did you want to take on next? What was important to you both in terms of research and as a professor in your capacity as a mentor to students?
Just to repeat: I had started at ETH well before that. Well, let’s put it this way: I like to be with young, bright people, and they know and they feel that I like to be with them as well. So, my goal was, explicitly or implicitly, to continue to do excellent science, with PhD students and undergraduate students, as you would call them. To be a good tutor on that level, and also to be involved in the broader aspect of teaching at the university. So there were quite a few aspects.
The first task of course, in terms of research, was to build up a laboratory, several laboratories. Infrastructure for crystal growth and sample preparation in general, including high vacuum thin film deposition. Infrastructure to do measurements and so on. So there were lots and lots of things to be organized so we could do measurements at the end, do some science with it. And the other one is getting involved in teaching, and in the broader aspect of teaching. One part of my activities were taking care or nurturing a research group with young talents, and the other one was being involved in the ETH-wide level of promoting good practices in teaching as well.
Within the Physics Department, later on I took on the responsibility as the director of studies, which is next to the department head function the most important job, in particular for the students’ education. So I was in charge of all of teaching activities.
To first start with our own group. I was fortunate enough to be able to hire a superb technician, Kurt Mattenberger, a friend of mine from my own student days. He was a technician then, and he remained the most fantastic gifted, universal, everything-knowing technician that one can ask for. Kurt was better than most doctoral/PhD students, by the way. Kurt would grow crystals during the week, and on the weekend could run the combine for harvesting grain for his farmer neighbor. He also managed many PhD students’ work very well. This was the first important thing I could do, is to hire Kurt.
Then I hired Janusz Karpinski and his two or three colleagues for materials synthesis. He’s an expert in high pressure, high temperature material synthesis, produces all these unconventional superconductors and other compounds of interest, such as MgB2 and inter-metallics. This way we could start right away with doctoral/ PhD students studying organic materials and superconductors.
The rather fast start was possible because I had been preparing it well before I fully came to Zürich in September 2000. So, yes, I moved into a freshly furnished office and the laboratories were also functioning, at least partly. Purchase orders had been filled for equipment. And then several wonderful young talents joined us working towards their doctorate/PhD. And so we got many good things going, including having international colleagues visiting us.
Other components of group life? How should the group work on a social level? Doing the scientific part is something students will learn, and I can teach them a lot. In some sense that’s the time consuming, but easier part. An equally important aspect is to nurture a group life that is not focused on the professor, not focused on me, but is focused on their collaboration. Despite the fact that they all had to do work on their own doctoral thesis, students also have the joy of interacting with each other, learning from each other, benefitting from others’ expertise and experience. And that component was emphasized a lot. Internal seminars, short presentations, regular tea time are a way to foster those interactions. And having lunch together, prepared by one of the group members. A poster on the wall summarized it succinctly: “We work hard and play hard.”
Our students liked to be together. They did not feel they want to leave the place, knowing that harsher life is waiting for them in the new workplace. They had such a good life doing science and having good friends that sometimes I had to stimulate them to move on.
Was there a point when you got back to ETH, when something was fully accomplished, as a researcher, as a mentor? Healing is obviously a process that can never be completed, but was there a certain point where you felt you could move on with your life? That this was not central to the things you were thinking about?
Yes, in the sense that at some point I realized—and it might sound strange—that my contributions to high temperature cuprate superconductivity were done. While I was much interested in observing what was going on, I also knew that the type of next questions that need to be answered or investigated are not what I want to do, or that I had the capability to do. Put it in a general way, I rather like to work on the first chapter than on the last chapter of a book.
But this is a personal preference. Highly respected colleagues get enormous satisfaction out of dotting the i’s and crossing the t’s, and then the chapter is closed for everyone. So I think it is just a preference of what people think is more suitable for them. I thought new things would be fascinating for me.
Like what? What else was new at this point? High-Tc is in the rearview mirror. What’s the frontier for you?
The frontier became multifaceted: charge dynamics, Seebeck effect and optimal device performance in organic molecular crystals; new superconductors, including MgB2, osmates and the Fe-based family; heavy Fermions in very high magnetic fields, Co-perovskites with charge ordering and magnetism, and other topics were high on the list at ETH.
One more frontier: in terms of a new experimental approach, we have systematically developed and demonstrated the immense power of microstructuring and contacting samples of all kind using a focused ion beam. This FIB technique has opened new frontiers in the study of superconductors and all kinds of correlated electron systems, and also other types of materials. FIB microstructuring has become a much-appreciated way to study emerging electronic phases in quantum materials, to use contemporary language. A lasting contribution, it appears.
Here is another aspect about frontiers in physics: While I was director of studies for some six years, I had the pleasure to chair some 250 PhD defenses in physics. At that occasion it became clear how enormously rich physics is, in the broadest sense, and also which particular important role condensed matter physics has to play in the interaction of physics with society in general, in bringing benefits to everyday life. I think it will have a strong base in creatively making new materials, and tweak them to do what fascinates us intellectually, and also leads to useful applications. In the long run, usefulness is welcome. In that sense we also do have some responsibility to cultivate the connection to society. Yes, it is fascinating to investigate and talk about black holes, dark matter and dark energy. That’s wonderful. I think bringing the benefits of physics also to the daily life is just equally important.
To state the obvious, all applications must be born in basic science. It is the prerequisite.
Let me expand your statement, which I fully agree with. Our director, Bob Laudise, the person I mentioned before, used to say, “Everything has to be made out of something.”
I love it. [laugh] Including the universe! [laugh]
“Everything has to be made out of something.” And in a sense, he captures why, condensed matter physics and materials science are an integral part of the human endeavor. Of course, there are ups and downs, and there are more important seasons and less important seasons, there are springs and summers. In retrospect I was fortunate that my career coincided with springtime and summer, represented by high temperature superconductivity in general. And I wouldn't want to have missed it.
Talking about fortunate circumstances, I like to mention that I was privileged to meet numerous outstanding physicists. That made a big difference in teaching. When teaching advanced courses, in particular the popular Physics in the Smartphone course that I had developed, with student involvement, the students realized that I was not quoting a textbook. The students realized that I am first of all enthusiastic about physics, and I could capture that enthusiasm and carry it to them in the classroom. They appreciated my firsthand experience, not only with physics but also with the physicists behind it all. So combining physics aspects with physics people who made physics happen is one aspect that I found very, very beneficial in teaching classes.
Now a short anecdote about my involvement in teaching on a wider scale. Back in 2005 ETH was celebrating its 150th anniversary. A full day was dedicated to new ways of teaching, and I had worked on the organization for two years. Every professor and all students could participate, as all classes were canceled. One of the lasting impact was the introduction of the Golden Owl Award, to be given to the best teacher yearly in every department. The political landmine was that the Rector/vice president for teaching could not possibly made the selection, as the faculty would not go along. Therefore we invited the student organization to organize the survey. Ever since, the Golden Owl awards are presented every year at the Academic Day, the most prestigious ceremony at ETH Zurich. In this way the importance of good teaching is emphasized even at the high quality school as ETH is. At ETH, I was not doing only science with the people in my group, but also trying to influence the teaching on a much broader level in the department, and ETH wide.
Bertram, now that we've brought the conversation right up to mountain biking, for the last part of our talk I’d like to ask a few broadly retrospective questions about your career, and then we'll end looking to the future. So the first thing I’d like to discuss—we haven't really talked about it yet—and that is the theme of technology, and the way advances in technology have been most relevant for your research. And that’s broadly conceived. By technology we can consider instrumentation. We can consider computers. We can consider modes of communication and materials. What sticks out in your memory as most important in terms of technological advance?
Well, there is a straight answer to that, and I start with data acquisition. When I came to Bell Labs, John Rowell and Bob Dynes plotted the tunneling spectra with a special X-Y recorder directly on paper and everything went from there. Perfect.
First, I introduced electronic data acquisition. In this way, I could do much more with the same information afterwards. First, I got myself a Hewlett Packard computer that had an HP-IB interface bus that has survived as IEEE interface. It could read out several multimeters at the same time. And later on, in order to do other experiments, I got myself a DEC PDP-11 classic mini-computer, with advanced data acquisition boards.
In terms of equipment, I had one of the very first commercially available Quantum Design SQUID magnetometers, with a single digit serial number. Later on I signed more than half dozen purchase orders for similar machines. This first SQUID magnetometer was ultimately essential for our work on superconductors, because magnetic measurements in low fields and on very small samples were possible. This way, I could trust the Meissner effect data quantitatively on samples with superconducting components, when we searched for new superconductors.
Spectroscopy is another example. While I had studied optical properties of solids in my doctoral work at ETH, at Bell Labs I set up a Raman spectroscopy lab for high pressure studies in diamond anvil cells. Structural phase transitions were the main topic. Many more advances in instrumentation came later on.
And why spectroscopy? Why do you single out spectroscopy of all the things you've worked on?
Because I used to do spectroscopy already in the mid-1970s. Since then, the spectral range and sensitivity of detectors had much improved, together with read-out and data acquisition. Everything has become more compact, because of the technology of building gratings or building prisms. And there’s so much built in electronics, pre data acquisition, that doing spectroscopy is so much easier and more efficient now than it used to be.
Another example is high pressure. Nowadays, doing diamond anvil high pressure experiments, producing recently room temperature superconductivity, is not as challenging as it used to be. When I worked with diamond anvil cells I broke quite a few diamonds. Diamonds are not forever.
And when we did Raman spectroscopy, we first had to build those cells ourselves. Nowadays, even that technology is much more advanced and commercially available. That’s another example. The availability of extremely high magnetic fields and specialized neutron scattering facilities are further examples of game changing developments.
Bertram, I wonder how you might reflect on contextualizing the ongoing mysteries of high-temperature superconductivity with some related mysteries in physics. In other words, supersymmetry might exist if we build high enough energy accelerators to get there. But it might not. We know that dark matter is there, but we don’t know what it is. How do you see the mysteries of high-temperature superconductivity in the sense of being able to detect it, or being able to theorize it?
In Phil Anderson’s words: “more is different”. What are all the new phenomena that can possibly emerge due to the interaction of many electrons? Actually, I'm quite optimistic that the level of detailed knowledge about high-temperature superconductivity in cuprates, and perhaps in other systems such as bilayer graphite, leads to a detailed understanding of how it emerges out of the strongly interacting electron system. In other words, it seems to be less of a mystery with all the detailed information we have. The situation appears way too complex that a single paper would be able to capture it all. There’s no BCS equivalent paper to high-temperature superconductivity.
Why not? What can BCS do that superconductivity cannot?
No, no. Electrons are paired, of course. A specific aspect is the d-wave pairing. I'm more alluding to what are the microscopic mechanisms that lead in this particular circumstance to this particular unusual pairing symmetry, and energy scale at which the pairing occurs. All in the context of understanding the over-all phase diagram with the various broken symmetry phases, starting out from the Mott insulator. Dealing with this broad question in a single paper might be asking for too much. I'm afraid it might be a complex paper, if it ever will exist.
To close out on a positive note, with the Schön investigation, to the extent that you've paid attention, in what ways has the outcome been a benefit to the field? What protections have been put in place where you might be confident that this terrible episode will not be repeated?
Well, let’s try to end on an upbeat tone. I would guess it is the learning process of what could happen, and the opening of the eyes of people in science. The experience that human beings, with all their beautiful qualities, sometimes can also be misguided even in the scientific environment. And that insight results in various consequences in terms of being attentive and putting appropriate checks and balances in place. And so, well, it means that once again the scientific process is a deeply human activity. And many things, perhaps on a much less dramatic scale, can happen when undesirable human traits overcome scientists in their work. Just look around and see the complaints about not being properly cited. Or visit a laboratory to observe how people interact with each other as human beings. They can be jealous. Might be able to try to compromise here and there. It is the human aspect that is unfortunately, I would say, but naturally, part of the scientific process. And this insight, as natural as it should come, sometimes comes at high cost, as we experienced. It’s just a human enterprise.
I come back to teaching and connection to human stories. When we teach basic physics, such as the propagation of an electron in a periodic potential, we know to take Charlie Kittel’s textbook or Ashcroft and Mermin and write down the derivations. But in terms of capturing the fascination of the student audience, it’s only half as exciting as if I tell them the story of the Gorilla Glass on their iPhone. The Gorilla Glass is the first glass ever, according to Corning, the ingredients have been mixed up following basic ideas of network topology that our colleague Jim Phillips had developed at Bell Labs. When I teach Gorilla Glass physics and tell them stories about Jim Phillips—he was my office neighbor—and how we interacted, and how he came about to get these insights, this is thousand times more fascinating for the audience than me writing down some basic formulas.
This is the positive human aspect of telling students how science is being done, with all aspects of being more or less perfect. Yes, science is a human enterprise. Research at the forefront will take a long while until everything is written down and cleared up. But then it’s boring. The fascinating part is to figure out what the hell is superconducting in this mixture of green and black stuff. And it turned out to be YBCO 123. That’s the fascinating part of it. Science and physics can be so much fun.
Last question, looking to the future, I'll return back to the question of applications and the satisfaction you currently derive and would like to derive about the societal value of all of this research. So in some ways of course your answer was going to have to be speculative, because it will be forward looking. But in what ways are you confident that all of your research, the entire body of your collaboration and discovery, ultimately will make its way to materials and applications that do have long-lasting, societal positive impact?
I guess you ask this question to other guys as well.
And some of the answers I did read, actually.
[laugh] So you're ready.
I didn't spend one second trying to find a novel answer to that. Look, in terms of cuprate superconductors, I wouldn't be surprised if on some level, microwave communication filters will be used more frequently. We had demonstrated this long time ago when the wireless phone call was transmitted over a superconducting microwave filter from another Bell Labs location in NJ to Bill Brinkman’s office at Murray Hill.
It is also very gratifying to follow the steady progress in cable technology at several places in the world. The next will be a 12 km long high voltage in-ground power line in Munich proper, called Superlink. Research magnets with cuprate superconductors also exist, and applications in wind turbines for weight reductions are also explored. All these are good reasons to be very optimistic about applications of superconductors.
So I would feel not very comfortable predicting in detail what will happen, and like to mention a little surprise. We have patents and publications on manganese oxides, colossal magnetoresistance materials, speculating that they might be used for memory devices or sensors. Who knows? Actually those papers—and that’s the surprise—on spin polarized inter-grain tunneling, and electron-lattice coupling, are even more frequently cited than our superconductor favorites. I don’t know why! It’s not predictable.
In the broader context, we think about organic semiconductors. Nowadays, we can buy gigantic flat panel TVs, displays, and they often involve OLEDs, organic light-emitting diodes. I don’t say that I contributed to a particular material there, but it is the type of basic understanding of what makes a material do certain things that ultimately will end up in an application. All that research is now being exploited on a huge scale, mainly by South Korean and Japanese companies, and others as well. I think there are only a few of manufacturing plants in the United States or in Europe applying this technology. However, I would guess that a large fraction of the underlying science of the OLED displays does come, and did come, from basic research done at universities and other places in Europe, in the United States, and other places in the world.
In general we cannot control where exactly our basic knowledge will diffuse to, and which company will translate it into an application. Within Bell Labs and the huge AT&T corporation that may have worked, say, 50 years ago. All activities, from research to manufacturing, were fully integrated and the company had all the time to wait until the engineers managed to translate new insights into technology. Nowadays, it’s a different style of translating research results into products.
And I wonder what will come out of all the research on quantum computing, for instance. I'm not an expert in that at all, but I wonder which company, at the end, will actually benefit most from all the great research at universities. Who will make the big money on it? But if we would stop thinking about new science based on which company might benefit from it, I think it would have a quite negative impact on our activities.
You mean those considerations cannot be baked into the discovery mode? That has to come after?
I think so. I think it was always the question in the context of why AT&T would have Bell Laboratories that costs so much money. Well, we look back and see what came out of it. Not just the Nobel Prizes, but many, many new technologies. Not to mention all the highly trained and successful scientists in many fields who went to universities to educate the next generation. Thus, it is very difficult, if not impossible, to make the connection between somebody’s latest discovery and the potential future application that benefits society. The path is very diffuse, and it might be very long.
I'm only aware of a very few examples of rapid deployment, and the most prominent ones probably are the LEDs, the light emitting diodes, that have revolutionized illumination everywhere. The invention of the blue LED, honored with the Nobel Prize there, followed a clearly defined goal and purpose. The time between this invention and its application in everyday life around the world was incredibly short, and we all witnessed it. But I guess this is the exception.
Bertram, it has been a great pleasure spending this time with you. I am so glad we were able to do this. I'm so glad Alice White connected us. And I'm so happy that you were generously able to share all of your perspective and insight with me. Thank you so much.
Thank you, David. It was my pleasure.