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Credit: Weizmann Institute of Science
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Interview of Moty Heiblum by David Zierler on May 3, 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 Moty Heiblum, Professor of Condensed Matter Physics at the Weizmann Institute in Israel. Heiblum discusses his current work in mesoscopic physics and he reflects broadly on the interplay between theory and experiment in condensed matter. He recounts his family's travails in Europe during World War II and he discusses his childhood outside Tel Aviv. Heiblum describes his military service during the Six Day War and his education at Technion. He explains his interest in focusing on integrated optics for graduate school, and he describes the convoluted path that led to his research at UC Berkeley. Heiblum talks about his postdoctoral transition to solid state research at IBM Labs, and he explains his decision to return to Israel and to build up a solid-state program at the Weizmann. He describes his longstanding interest in the quantum Hall effect and his fascination with turning electrons "on and off." Heiblum discusses his group's contributions to quasiparticle research and he reflects on receiving the Buckley Prize. At the end of the interview, Heiblum conveys his motivations in building devices, he describes the "eureka" moments in his career, and he explains his future focus on exploring the possibilities of working with gallium arsenide.
This is David Zierler, oral historian for the American Institute of Physics. It is May 3rd, 2021. I'm delighted to be here with Dr. Moty Heiblum. Moty, it’s great to see you. Thank you for joining me today.
Okay, happy to be here.
Moty, to start, would you please tell me your title and institutional affiliation?
My title is a professor. Full professor, for many years. And I am here in the Weizmann Institute of Science in Rehovot in the Department of Condensed Matter Physics, which is part of the Faculty of Physics that contains the department. And I am one of them, sitting now in the so-called Submicron Center, that maybe we will dwell on it a bit later.
Moty, I take it you’re in your work office, not your home office, right now.
And the COVID situation is looking pretty good right now in Israel.
Yes, it does. Even though it was rather relaxed in Weizmann, because rather than going to a stringent quarantine, the management, very nicely restricted the number of people that could work, but allowed us to keep working, indeed slower, but all along the past year.
So, you have not really slowed down so much in terms of access to instruments or working with your colleagues or anything like that?
Well, we did slow down, because there were laboratories and specific tools that had been disabled, so we couldn't use them. We couldn't fabricate new devices. So, we slowed down, but we could in general measure ready devices in our own laboratories. But we were not stopped altogether. We could work.
Moty, just for a snapshot in time, what are you working on currently? What’s the big work in your group right now?
Well, I'm working in a field which is a subfield- okay, the general name, I would say, is called mesoscopic physics (laughter). And in a way, it’s a quite similar to the work described by Bert Halperin in a previous interview. It may be referred as “the god” of the general field. I'm an experimentalist and Bert is a theorist. Bert, is broader than I am. Being an experimentalist, I have to work with specific tools and specific materials, while Bert can fly anywhere he wants. The “meso” is “in between.” It’s not macroscopic physics, which is just all the way from stars to a table. And not microscopic physics, of atoms, molecules, etc. But yet, behaves according to quantum mechanics. Indeed, everything behaves according to quantum mechanics, but in most of the effects the quantum effects are washed out. We don’t feel that this table is really composed of many molecules. Each of them obeys quantum mechanics. Because it’s part of the environment, and there is a lot of disturbance, and you don’t see really the quantum effects in the wood. But when we work with our devices, which are not microscopic, they are mesoscopic, we see quantum effects. All the time.
So rather than working with atoms, which are an angstrom size, which is a tenth of a nanometer, we work with something which is in the range of a micrometer. But still we get a lot of physics out of it. So this is, in a broad sense, what my group is doing. And the point is that the main subject I've concentrated in, at least in last years, is a phenomenon called the quantum Hall effect. I don’t know if you're aware, but I was awarded the Buckley Prize on the effort, with the citation was specific on the quantum Hall effect. This was an amazing discovery in 1980, by Klaus von Klitzing, which developed and grew to multiple sub-fields, with one of them is the fractional quantum Hall effect. The latter, hosts many different quantum states, with every one of them behave differently. As we study these states, we understand how peculiar or how important they are, in the sense of fundamental science, and maybe also in future applications. The work we do here may serve at some point, being less vulnerable to disturbance from the outside, in some form of quantum information. I think it’s a broad way to describe what we do here.
Moty, a few very broad questions before we go back and develop your personal narrative. You mentioned Bert Halperin, of course, as a world-famous theorist. I wonder if you can reflect broadly in your career, in your field, when has it been obvious that theory has been leading the experiments? And when have the experiments been leading the theory?
That’s a good question. I think in my role, most of the time, there were predictions, theoretical predictions, which we went ahead and verified, in actual structures. But the thing that was more interesting and exciting that we stumbled on unexpected physical behavior that even to this day are not understood. But I would say most of the time, there were predictions that we proved them right or wrong. For example, we can go into it later, that we are measuring now, as we speak, a quantum state. And the quantum state, even predicted by Bert Halperin, is a part of a family of states, named non-abelian states. This family has, say, nine members. So, theorists expected that the studied quantum state is a particular family member. Indeed, we proved that this state is a part of this family, but it’s not this son; it’s a daughter (laughter). So, it’s not the member that was predicted. And then theorists got rattled, and went back and calculated, still declaring that “It’s impossible. It cannot be.” So, from the first experiment that was published in 2018, that we showed it, we performed complementary experiments, with the first was submitted to Science, that claims, “No, we are right. You are wrong.” With still objections, now my student is in the lab and is measuring the third configuration, and again, he seems to find, again, the family member we found before (laughter). If you trust your measurement, then don’t shy away!
Another example, many years ago, people say, if you measure in the fractional regime, you will find particles that behave as a fraction of the electron. One third, one fifth, etc. So there, we went and measured and found out, indeed, the one fifth and one third of it. So here was a prediction, and we verified it. A counter example, we found bunching of electrons, namely, two electrons come together, and they like to be in pairs, though they like to repel each other. Presently, nobody understands why it is the case. Even after two publications, the phenomenon is still not understood. So, the beauty, I think, of this field, is that there are many phenomena to be studied yet. It’s a mature field but still an open field for new studies.
Moty, a question about names. What is your perspective on the transition from the field being called solid state physics to condensed matter physics? And where is soft matter physics for you in that transition?
Initially when I arrived at Weizmann, it was solid state physics. And then, with liquids added it became condensed matter. And soft matter are somewhere between this and that. So, when you say condensed matter, I think this word is encompassing basically a larger variety. Even though the department that I am a part of deals with solid state physics.
Moty, in terms of your overall motivations, what is the rough balance between basic research and applications for your research? Where are your motivations? Where have you seen reason to make patents? Where are you just concerned about discovering how nature works?
It’s the last one. I maybe have two or three patents, but I'm not after them at all, and my main motivation is studying fundamental effects of physics. If you want to say, “how nature works,” I agree. I get less into applications. In particular, the work we do is at very low temperatures. We are working with temperature of close to absolute zero, which makes it less applicable. Even though many people talk about quantum computers with these very low temperatures now, et cetera, but still, it is more difficult than just this desktop, okay? If something will happen using our understanding and could be useful, I'll be very proud. Even though my education was in electrical engineering, not in physics. Also, Fermi was an electrical engineer by training (laughter).
You're in good company (laughter).
Yeah, right. So, all my studies, BSc, master’s, and PhD, and later I worked in IBM, as an electrical engineer. So, one would think that you would be inclined to do something practical. But I shifted over the years. As a matter of fact, I really never thought of doing something that would work, or something like this. I was always interested in deeper understanding more. Because every time you find something, you say, “Oh, I understood it.” But then you see that you don’t understand it.
My work is somewhat of climbing on a tree, and there are there are branches, and you pick a branch, and climb up. If you don’t take this branch, but another branch, then you will open something else. And I think that the beauty, or at least the situation being in university, and in particular here at Weizmann, that you can do whatever you want. Of course, you have to bring your own money, most of the time, so you can support the students, the postdocs that you have, and buy the equipment, et cetera. There is a lot of work in getting money by writing grants. But other than this, nobody tells you what to do. This is in a way an unbelievable freedom that I couldn't think about in any other place. You could be in a startup and have the pressure always of the investors. Here, the pressure is only internal. The pressure is internal, that you want to achieve more and to understand more. And as long as I come in the morning to the office excited, wishing to see what’s going on, I feel in a way blessed, to have this opportunity.
Moty, for our mostly American audience that’s not familiar with the Weizmann Institute, I wonder if you might explain how your research group fits in with the overall mission of Weizmann.
So, Weizmann doesn't have a mission. Weizmann Institute is a very special place. I arrived here some thirty-two years ago, after being in IBM Research Center. Weizmann is only a graduate university. That’s the reason it’s called an institute and not university. We don’t take undergraduates. We have only graduates- master’s, PhDs, and postdocs. And it’s all concentrated in a few faculties, chemistry, physics, computer science and mathematics, and biology. Each is divided into departments. The number of students is rather small, because they are only master’s and PhD. Moreover, you are not obliged to teach. So, you can devote most of your time to work. To work in the lab. To work with students. It is the only Institute in Israel. But there are similar institutes in the United States. When I considering coming back home—because I was born here, there were few options in universities. I’d never been in Weizmann before. I passed by the gate or something like that when I was young, but I didn't go in. This was a very important decision that affected my life throughout.
Moty, 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.
Okay, so this is going to be a bit emotional. I am a second-generation Holocaust boy, or man. They came from Poland. They came in 1945. They lost all- okay, my mother lost all her family. No brothers, no sisters, no niece, no nothing, no parents, nothing. My father had two brothers that survived, and a nephew. They lived in France. My parents were born in two small towns is east Poland. They moved to Warsaw. And then they got married before the war, in 1938, in Warsaw. They stayed in the ghetto during the war with their families. They went out of the ghetto before the uprising. They survived being- with falsified documents in the Christian side.
They came to Israel in 1945, with the first boat that came after the war. I was born in 1947, just about two years after they arrived. We lived in a small town, which is about twenty kilometers south of Tel Aviv, called Holon, in Hebrew “sand city.” In my youth I grew up in this place. I have a brother, who is eight years younger than I am. But when you live with Holocaust survivor parents, with all the neighbors are similar, it affects you strongly. So, all the children that were born around my time, lived, in a way, together on the street. And when you live in a place like this, with parents that went through something that’s unbelievable, that I don’t think that I would be able to survive through it, it is not easy at all. You inherit, I would say, anxiety. You are scared. Even though there was nothing to be scared of.
I have been influenced mostly by my mother, that always said that she was the best in her class, and she had to leave, and she couldn't continue studying (laughter). She had to leave sometimes toward the end of her elementary school, to help the family (this was before the war). Consequently, I had the duty to continue what she could not. Okay? What she did not achieve. So, this is subconsciously stuck in me all the time, until today (laughter). Even though my parents are not alive, my mother died in ’87, my father in 1990, she was a very dominant person in my life.
My father basically was a more simple person than she was. He was working, bringing food home. He was very emotional. And she was a strong woman. Very small woman (in size). And she basically drove me all the time in my studies. At the time I thought, “Uch, it’s so bad.” While the kids in the neighborhood played outside, I had to do homework and study. It was a continuous pressure. And this probably affected my adulthood. The only thing I can say, that I decided, as an adult to do exactly the opposite. As another example, my mother decided that I should go to a professional school before the Technion. Namely, if I won’t be accepted, at least I will have a profession. So I studied engineering. It’s called like technical engineering (laughter). And of course I had to go to the Army for three and a half years. Everybody had to go. So at least then you're out on your own.
But in a way, even today, it’s very interesting, because when I have something that I'm successful in, I wish that she should see this success. Also at night, when I am awake, in the middle of the night, I think about her. She died too early to see a lot of the fruits. In 1987, when she died, I was still living in the U.S. I came back in 1990. I was doing okay over there, but nothing compared to what I got involved with over the years that passed. So, I think that I'm part of the called second Holocaust generation. This slice of the population has some common denominator, of achieving and suffering (laughter). Suffering, mentally I would say, because all of us were born years after our parents arrived from Europe, and somehow it permeates. Being young at home, it seemed like a gray cloud throughout. We didn't speak much about the past. Sometimes a bit of information came out. Other times, my parents didn't want to talk about it, because we won’t be able to withstand the truth, the picture of hell. So, I know only a few stories, not very many. Now, in retrospect, I would sit down and ask, “Tell me this, tell me that.” I don’t know if this is exactly what you are looking for in your question.
Moty, is your sense that your families from Europe, were they more secular, or were they more religious?
Secular. Totally secular. You see, I even remember this. Sometimes it’s not so nice to say, because my mother always told me, from day one- first of all, she didn't know how to name me. So, the first story she told me was that she had me, and she didn't give me a name. And her father appeared in the dream and was very mad at her. And she didn't know because she didn't want to name me after her father, because she never saw him die, he just disappeared. And she didn't know, maybe he’s alive. You know, people would be looking for relatives for years and years later. Sometimes they found them. And then he was mad at her for seven days, every night, until she decided that he’s telling her something, and she decided to call me after him, Mordehai. And then she start sleeping. And that’s the story.
And then when I was older and knew something about it, there was a synagogue here and a synagogue there, she didn't let me go to a synagogue. Even though we went to play around the synagogue when we were kids, she didn't like me to go to a synagogue. She says, “God is not there. There is no God.” There was no God. I did my Bar Mitzvah, also, because all the neighbors did it, and I did it, too, and I learned how to sing my songs. But she was very anti [religious]. She was eating freely on Yom Kippur. She closed the door. She didn't want anybody to see. She didn't want to poke somebody in the eye. But she was very, very anti religion, she said “God cannot exist. God cannot exist.” And I am totally secular, of course.
Do you think, Moty, that your mom’s views on religion were influenced by the Holocaust, by the Shoah?
Of course! Of course. Her father was super religious. If you see pictures, he was like a black [hatted] Jew with a beard. I have a picture. No, they studied the Talmud and all the household was religious. Total religious. Like in many small villages in Poland at the time. No, the Holocaust changed her totally. She was near death many, many times. She was going from the Gestapo somewhere, and she was expecting a bullet in her head. So, no question about it. She didn't say, “There’s no God.” She told me why there’s no God. “How can be God if something like this happened?” So, I was born, and I never was connected to religious. And even especially now in Israel, when the country is very divided between secular and Orthodox Jews.
Haredi. And the tragedy that happened now a few days ago (in Miron mountain, when forty-five Haredi Jews died [in a stampede]). So, this is sort of like two countries, two places. I have nothing to do with them, and they have nothing to do with me, and we are separated where we live and growing up. And so it affects a lot, really, my political views, and the way that I live in this society that is so fractionalized. We are all Jews. Okay, fine. So, I'm a Jew, okay. So, I don’t know if I feel- I feel Jewish because I was born Jewish. Okay, I studied. I have something. I like to read the Bible here and there. I like to read through history or go over to the West Bank or Jerusalem or so. I'm connected to this country. But I have no microgram of religion in me at all (laughter).
Do you own tallit and tefillin?
No. Never put it on. Well, I put them on when I was a Bar Mitzvah. But I never put tallit on. Was asked more than once, “Oh, come, come on. Put this—put it on. Put it on.” No, no, I never did.
Chabad would love to meet you.
Oh, they meet me! At the airports. They meet me everywhere. All over the place.
Moty, what was your first language growing up? Was it Yiddish or was it Hebrew?
No, no, it was Hebrew. But I understood Yiddish, and I even could speak. Now, I cannot. And when my parents wanted to converse without me understanding, they spoke Polish. So, I didn't know Polish. But it was Hebrew all along.
When did you start to get interested in science?
It’s a good question. There were these books that my father bought in the 1960s. It was called The Young Technician. And they have all kind of little games to play, and things to build. That excited me a lot. I was building a transmitter or the little radio or things like this. And I studied later in the professional school that taught me how to be a technician. So, I knew something about it. So later on, electrical engineering. And even before all this, playing around with tubes and things like this at home. So, I don’t know. I always liked more physics, mathematics, engineering, and things like this, from youth. Now, I think that maybe I should have read more literature or do more humanistic stuff or so. But I was from very young age, even though they were not.
My parents were not professional. My father, he had a store. He had a place that he fixed tires, for buses and cars and stuff like this. And my mother, she did some hats, and she sewed some hats, and she sewed clothes for people. But she didn't work. She was at home, taking care of me and my brother, eight years younger than I am. So, she was sitting on my neck all the time (laughter). “Do your homework.” It’s very interesting, because all the time when I was doing homework or so, there was some food near me (laugher). So, I was a very fat boy when I was young (laughter). I was overweight. And this is part of the problem, also, that other kids were laughing at me, that I was fat. And between my legs, I had holes in the pants, which was my legs, they were scratching each other. But this I think is- the reason that if you sit and eat, you have to finish what’s on your plate. Just there’s no way that you cannot. So, a plate comes in, you eat, it goes away, another plate comes in, and so. So, you could never throw away anything. You have to finish the last drop. When I was young, I was super upset, because sometimes you are not hungry. But you have to finish it. When I grow up, I understand the problem that she had all the time, of starving for many times. And now, there is a bounty of foods. They're plentiful. I lost my weight when I went to the Army. When I went to the Army, I was eighty-four kilos, which was not terrible, because my height was one hundred and eighty or one hundred and eighty-one, so not bad. But now I am seventy (laughter). So, it was another fifteen kilos, about.
What years were you in the military?
From 1967—and this is an interesting story. This is the Six Day War. But I entered the Army just as the war started, the Six Days War, so they didn't know what to do with me. I was just sitting in a base, and I was painting trees, white color. And then I was in the Army for three and a half years, from 1967 to 1970. Seventy-plus. And then at the same time, since I was based in the North, so I start studying in the Technion up in the Carmel Mount in the evenings. So, I could leave in the evening the Army, go up, and those two first years in the Technion were equal one year. And then I studied three years later, continued three years later. So, I was three and a half years in Army.
Where were you during the Six Days War?
So, the Six Day war, on the six days- okay, so I was at this base and they didn't know what to do with me (laughter). I didn't know how to hold a rifle. So, they sent me home every night (laughter). And I didn't want to go home! Because how can I go? A soldier goes home and people are dying in there? So, I wait until like dark night, and I went home, very dark at night, and left very early in the mornings, because I was ashamed to be a soldier and be around, and not fight. So, I was in a base in the middle of the country. And only after this, they started the basic training and all the things. And I found myself eventually a teaching technician. That I'm dealing with the communication tools. Because I can, with this background of an electrical technician before I went to the Army. So, they used me as- basically I became a teacher. A teacher, and I fixed instruments and stuff like this. So, I never fought, which I was very happy about.
Tell me about your decision to attend Technion.
Well, it was quite normal, because at the time, there was no electrical engineering in no other place. There was only Technion, in this time. Tel Aviv University started a school. But the only place to go and do electrical engineering was the Technion. The reputation of the Technion was excellent, and I was accepted. I married very early, also. At the time, we married early. I married when I was twenty-one. And we had a child when I was twenty-two. So, I had to work. So, I was studying at the Technion, and there was a school attached to the Technion, inside the border of the Technion, a professional school for engineering. So, I was teaching there also at the same time, so I can support myself and the family at the time. When I look back how I did it, I don’t know how I did all these things, my own homework as a student, my exams, and then teach, and then later on correct exams for students or so. I cannot believe now. It’s too difficult. But the Technion was very normal thing. If you want to do electrical engineering, you go to Technion. That was the place.
In the United States, many electrical engineering programs are more or less applied physics, at places like Harvard or Berkeley. Was that your sense, that it was in some ways an applied physics program?
But you see, this was an undergraduate. So, the undergraduate, you just study. And I picked- the first couple of years of math and things like this, everybody does. Physics, et cetera. But later on, when I had to choose, I picked more semiconductors. I liked more the semiconductors, the solid-state physics. I already was drawn into it. I don’t know why. I don’t remember why it drew me more than to study communication or all this stuff you could do, optics or infrared or there were all these courses. And I liked very much to see it, to feel electrons moving in a solid, what happens there, and so forth. Maybe it was because of with my education being an undergraduate in the technician school, if you want to call it this way. So, when I finished, toward the end of my five years, because the first year was two years, five years in the Technion, I knew that I want to go overseas. I want to study, go, fundamentally or so, in the U.S. I didn't want to stay.
Was the program at Technion geared towards experimentation? In other words, if you wanted to try out being a theorist, was that available to you?
Yeah. Sure. Look, we are talking about late sixties, early seventies. The thing is that they wanted me to stay and do a master’s there, very much. If you go and do the master’s, you can choose if you want to work with a theorist or with an experimentalist. But the Technion was fairly strong in communication, theory of communication, et cetera. And there was not very much in solid state physics. We called it at the time solid state physics. Not very much at all. So, the only place that I thought I could do more was overseas. Even though I find myself not doing much solid state. But the idea was that I would like to do solid state. Because there was nothing like that at the Technion.
What advice did you get specifically about needing to go to the United States? In other words, why could you not stay in Israel to pursue your graduate research?
Well, that’s what I'm saying, that I wanted to work with solid state physics. And there was another buzzword at the time that is called Integrated Optics. Because there was integrated electronics. So other than having integrated transistors we'll have optical devices, and light can go through little channels, et cetera, et cetera. And then I thought, “Maybe I'll study this.” And there was nothing like this in Israel. So, I thought- or I'll do solid state physics proper or look into integrated optics. And somehow- I had a child already. Somehow my wife agreed with me, and we decided to go overseas, to the United States. I applied. I was accepted. I think I applied to ten places. I was accepted in two or three. And I went to Pittsburgh. I could have stayed there and my career maybe would take a different route, but—
Why Berkeley? What was interesting about Berkeley for you?
Okay, so I didn't go to Berkeley right away. It was a bit- it’s also a story (laughter). Everything is a story. So I went to Pittsburgh, to Carnegie Mellon, and I was there for a year. Somehow here, you get a master’s and you don’t have to do a thesis at all. And people were very nice, very warm, there. We were adopted by a family, which helped in the assimilation. But then I decided that I don’t see a future for my intentions in science. And I moved on to the University of Washington. Because then there was this person, Prof. Jay Harris, was doing integrated optics. In parallel, I applied to Berkeley, and I applied to Yale, and I applied to University of Washington. And then I decided- I was not accepted in Yale, but I was accepted by Berkeley, yet, I decided to go to the University of Washington in Seattle. So, I picked up the family (had a daughter at that time), and we crossed the country, and we went to Seattle. And what happened there, that in three months that I was there—this was summer—my advisor, Prof. Jay Harris, got an offer from NSF to go and work in Washington. So, he came to me and he said, “I'm leaving.” Even though I already had a chance to write a paper when I was there in these three months. This was a terrible shock. And he said, “But NSF will support a student of mine any other place he wants to go.”
I wanted to go to Caltech. But the professor there, which was Israeli by the way, was ready to accept me only if NSF will him for three years, and not one year.” So- and then I receive a letter from Berkeley. I forgot about Berkeley at all. The letter said, “You applied for housing here. If you don’t answer in a week, then you don’t get it.” So, we have housing in Berkeley!” (laughter). So, it was just- I didn't know what I am going to do there or anything like this and was not sure any more about doing it in Berkeley. And then we have now dormitories for us. So, we went to Berkeley (laughter). And this turned out to be fantastic, because it’s a fantastic school. And then I did something like integrated optics. So, I studied there for four years, in the electrical engineering department. And then I took many, many courses in physics. But we were there from ’74 to ’78. And the thing is that these schools had been recruited heavily by the industry, IBM sent people. Bell Laboratories sent people. So, they came twice a year to recruit and find students that would go and work with them. So, in the four years that I had been there, they kept recruiting me all the time. So immediately, they told me, “Okay, you have an offer in IBM. And the other one said, “You have an offer in Bell Laboratories.” So in 1978, Bell Laboratories was much more advanced relative to IBM in the directions I was interested in. So, I got an offer two years before I even finished my degree.
Moty, who was your graduate advisor at Berkeley?
So, I had two of them. One of them was a young Prof. named Ken Gustafson, and the other one was a very well-known Prof. named John Whinnery. John Whinnery wrote the well-known book on electromagnetism (Ramo, Whinnery and Van Duzer). I worked with another graduate student, Shih-Yuan Wang, and we became friends. We worked together for four years. And so you see, in an unpredicted way I arrived at IBM. And I started—continued the idea of integrated optics somehow from wherever I started, from Pittsburgh to there, to Berkeley, and this and this and that. But very quickly, due to a different environment my goals changed.
Did you accept IBM on the basis that perhaps you would make a life for yourself and a career in the United States and not go back to Israel?
Yeah. I knew I'm going to start in the USA initially. IBM had a nice research center, and one could do whatever he wanted. So, I came to IBM. I also got an offer from Bell Labs.
Was IBM as prestigious as Bell?
Yeah. The research center in Yorktown Heights, called the IBM Watson Research Center. Bell Labs research was concentrated the so-called Area One, in Murray Hill, in New Jersey. Both research centers were competing all the time. I think in Bell Labs. had more Nobel Prizes initially, but IBM was successful later. I joined the group of a Nobel laureate at IBM, Leo Esaki who shared the prize in 1957, due to the discovery of the tunneling effect. To pursue my goals I left the group. It was a very difficult time for me at IBM for many years until my first important contribution in 1986. I was there from 1978 until 1990.
Moty, coming from graduate school, what did you see as your area of expertise? What were you able to contribute right away at IBM?
So, they gave me freedom to do what I want. I decided very quickly that I would not work with integrated optics, because this was a department of solid state. And the point is that when I arrived, I had some idea to make a new transistor, a new type of transistor. But for this, you needed material. And the material that I wanted to work with was not silicon; this is the common one, but gallium arsenide, which is really the basic for the red laser diode. But then there was no gallium arsenide there. There was nothing I can do. I wrote a theoretical paper describing my idea: a hot electron transistor. I had this idea when I worked in Berkeley, but it was an optical type transistor. So, I wanted to do it, but I needed material, and I didn't have any material. So I decided to grow the material myself. The system needed to grow such material is called molecular beam epitaxy. It’s a big vacuum system. It costed around half to one million dollars. I went to the director and asked him “I want to buy this system.” The reply was negative, as there was another group growing this material. And I said, “No, it’s of poor quality. I cannot use it.” So he said, “Well, try it.”
Desperately, I decided to leave IBM. Called Bell Labs. This was about a year after I visited there. Called Mort Panish, who gave me the offer, said, “Sure.” So, I went to the director and said, “Look, I'm leaving.” So, he gave me the money. I went for a week to the university of Illinois to learn how to grow gallium arsenide. I didn't know anything about it. It took me about a year and a half before I got it. So now we have only two and a half years and I have a system, and now I start going. But the idea is to do devices and physics and here I'm growing materials. The bottom line, I published less significant papers. I had only one technician and a summer student. I grew myself all the needed materials, and fabricated and tested devices. My first significant results came in 1986. Can you imagine from 1978 eight years later, I got my first Physical Review Letter, which was my first substantial paper. And in this work, I provided a direct observation of the ballistic transplant of electrons. Before, ballistic transport was only theorized. Namely, transport without hitting ions and phonons. If distance is short enough, you can achieve ballistic transport. All this after many years of work. If I would have been at university, I wouldn't get the tenure. The nice thing about this place is that they kept me, supported me, until I this result, which was not obvious.
Moty, why was it not obvious? To you or to them or to everybody? What was not obvious?
Well, first of all, I was scared. I was scared. I was dead scared, because nothing happened, and I failed and failed and failed. And the management there told me, “Well, maybe you do something else. Maybe you grow material for other people, because you don’t have your results.” So, it was a lot of pressure. I think I was half of the time depressed. Went to sleep early. And at the time, we had more children, all together four children. So, in 1986, I think I received the Innovation Award, in IBM after the observation of ballistic transport. And then, for two years, I was riding on this wave of success. Because I knew how to grow my own material, between 1986 or 1988 or something like this, I started paving the road return to Israel. And the reason to apply back in Israel, even though I thought at the time, you know, “Go back to Berkeley.” So, I applied to Berkeley, thinking, “I love this city.” But I don’t know, they didn't accept me, they didn't have room, whatever it is. But they gave me an offer in Cornell. They gave me an offer at University of Pennsylvania. But our parents got very old. My wife wanted to go back home. So, with this few papers only, from 1986 to 1988, I started interviewing. But when I came to a visit, there was desert here. There was nothing here. Weizmann Institute was a nuclear physics department. There was no solid state. The Technion had something with silicon and they said, “Oh, maybe you can take it and do something with it.” So, it was very depressing. And then I came up and said, “Look, I will build a center.” Let’s call it the submicron center, at the time. Submicron. And I want money. And I built the center.
Lucky enough, there was a new president Hain Harari, who took interest in what I proposed. And I said, “I'll come home in 1990. In the meantime, if you give me money, I'll start in these two years, between 1988 and 1990, to work on it, design it, order equipment, et cetera.” So, it was a lot of stuff at Weizmann to decide whether they want to start a new venture like this. But lucky for me, the department was nuclear physics, and nuclear physics was already a dying field. There was an accelerator that was very old. The faculty was looking for some other direction to go. And I came at the right time. So, there was huge argument, because I asked fifteen and a half million. At the time, Weizmann had a deficit of thirty million. There was a lot of argument on campus. You know, for fifteen and a half million, you can give to many, many scientists $50,000 and let them work, rather than to give it to one guy. But Harari did it. So, he agreed to collect the money. He asked me if I am for sure want to stay (laughter). I said yes. And if I want to leave, what can he do? No, he cannot put you in jail, but I told him that I'm going to stay. So, this started another difficult- so if I tell you that in the U.S. it was from 1978 to 1986, now we started to go from 1990 to 1994. Difficult times. Because this place that I'm sitting now in. the Submicron Center that was built, you build the whole building, buy the equipment. You have to hire new personnel and get students. Everything was new to Weizmann. So, when I came here, I told the president, “Look.” I came here, and one had to call through an operator. Fax to somebody. I said, “No. You give me a phone that I call overseas anytime I want.” I place an order, it comes out in two days. So, I have all these rules of how to spend this fifteen and a half million, and he gave me a lot of freedom (laughter). He say, “If you build a house with a building of gold, you will not have any money for the equipment. And vice versa. So do whatever you want. Choose it. Divide it.”
So, the time was tough because I was just building a building. I didn't build a building before in my life. I was the bank. I'm watched carefully the money flow. So, it was four years of no physics at all. And that wasn’t easy at all. It was very, very difficult. I didn't publish anything. I disappeared from 1990 to 1994. But I was lucky in a way that good students came in because it was exciting, and it was a new building and new technology and stuff like this. And so I was very lucky that fantastic, fantastic students arrived here. But I was almost alone. There was one theorist. But then this place start gathering people. People came from Russia. In 1990, there was the big immigration, and a million people came from Russia, among them many scientists. So, it’s just the time was right that in two years, a new department was formed. I formed the new department, Condensed Matter Physics Department. I was the chair, aside from managing this center. And I think the physics faculty started to change.
Moty, what was the process of attracting graduate students, given the fact that you were building this department from scratch?
So of course, the first year or two, the excitement part was that there were here master’s student studying. They came to study. There were at the time twenty-five master’s students every year. And they heard about the center and they came to interview with me. And then I told them that, “You're going to come, it’s going to take time, you cannot publish right away, but you will have a chance to participate in building a new center, from scratch. You will see all the equipment. So, when you leave later on, you know enough that you can build your own lab, also.”
So, I had a bunch of good students that started. And I had also help, because I got money to hire engineers and technicians. This was part of the whole deal, that I had. That I have some slots for about eight people, to run the different laboratories. But the students came in and they participated in building, e.g., the evaporators and the lithography labs. They just started to do it by themselves and learned to do it. I was just conducting all this stuff, for four years or so. So, publications started coming out, although slowly. But it was again another difficult time (laughter). If I look at the number of- in Israel, there’s an HMO. It’s called Kupat Holim. This is the reason also we are so vaccinated so well, because there are- it’s not the government does it, it’s the HMO do it. So, everybody goes to a particular- one of the HMOs. And I looked at my folder in this year it was this thick from all kind of stuff that I was sick (laughter). Everything pressure. Everything pressure related. I think that I'm dying here and dying there, and so, so- I don’t know if you know this story, The Giving Tree?
Okay (laughter). So years later, I went to a psychologist to help me out, and she said, “Your body is the Giving Tree. Everything here, you dump on your body. So, you're body say, ‘Enough!’” So, your body doesn't understand, “Why you dumping this thing on me?” “You made your body The Giving Tree.” I think the pressure was enormous because what happens is you get this money, you build the building, and am afraid to add a “white elephant” – as there were already two “white elephants” on campus. Many said, “The Submicron Center will be the third white elephant.” So, it was really- the pressure was- you have to prove, you have to show that you can make it. And the first few years were very difficult. Because you don’t show right away that the center will succeed. But these people that came, theorists that came, also from Russia, and also theorists that came here, it became sort of a place that people gravitated to it, because there was a facility, there were experiments going on. The theorists then can go ahead and talk to experimentalists or so. So, it took from 1990 to about, yeah, five, six, seven, years, that it’s only appeared on the map.
We were visible already. Not only MIT and Harvard or so, this department or, at the time, it was mostly Submicron Center, which part of the department, was already showing some data that was visible. And I think that the decision to come here also was in a way- it was nice, because first of all, you come here, and university takes care of you. I live on campus, and my home is 350 meters from the center, walking distance. So, I'm walking for seven minutes or so, and I'm home. And I can come here and go back, and I can go to lunch. I don’t have to take a car and drive home with traffic jams or in the morning.
We are now at a totally different place. I'm not the director anymore, because I basically reached my official retirement age that means in Israel, being sixty-seven year old. But what two administrations did until now, I was extended twice. I was extended to seventy, and now I'm extended to seventy-five. So now I have to see what will happen in the near future. Because I was productive, and they didn't see any reason that I should go, and I really appreciated it. Because for me, this is a big part of my life and my hobby, and the thing that I am thinking about all the time. Without this, well, I should prepare myself for the point that I won’t be able to do it, or I won’t be let to do it, and think about something else I will do. Because now, I have all these plans, and I come in on the weekend, and I work. For me, it’s a very big part of my life.
Moty, it’s such a unique opportunity to be able to build a department, even a building, from essentially nothing. What were the biggest research questions you had at the time that motivated you and gave shape to the way you wanted to build this program?
So, when I came, I had some kind of ideas that I would like to make interferometers, because you see, it connected to optics. Interferometer that we interfere electrons. And I’d be able to show the wave properties of electrons, by making- letting them interfere. But very quickly after this, I was drawn into quantum Hall effect. Because then there was this proposal that there should be the fractional charges, that I mentioned before. And this one, how do you measure the fractional charge, when the idea is, let’s measure the noise due to these charge. Because you have now fractional charges which are small, of imaginary quasi-particles. All the electrons together behave as if there are fractional charges. So, when you measure the charge, you measure fluctuation of the current proportional to this charge. So, we measured it. I had a postdoc from Russia. Misha Reznikov, who brought with him high-frequency techniques; otherwise I won’t be able to go into such experiments. Indeed, we found e one third of an electron charge, and later one fifths of the electron charge. So, I think that somehow, with fantastic students, I delved into the field of mostly quantum Hall effect. And in the quantum Hall effect, the current in the sample, which is a two-dimensional sample, the current moves along the edge of the sample. So, you can use these edge currents like one-dimensional channels of electrons. So, we start using these one-dimensional “wires” to do all kind of stuff, while guiding the electrons along the boundary.
So, one idea led to another. And I think that being an electrical engineer, the way that I thought and think about the work is different a little bit. Because a physicist in a way say okay, I have a chunk of material. I want to see what it is. So, I'll bombard it with photons, electrons, ions, whatever. Let’s see the response of the material to such experiments. An engineer should construct something. Let’s make an interferometer. Or, let’s make a device that will do have some function. So, the idea is to make a device, but when you do the device, and start seeing the operation, you start finding all kind of effects you didn't expect. So, I think that even though my background is mostly an electrical engineer, and I may lack fundamental parts of the theory, it paid off in a different way. So, the experiments that I ran, my good ones, are usually challenging, because we make very complicated structures that very few groups try to fabricate. So, I chose to work in these things not because the other stuff is not interesting; because I think this is my training, in a way. My self-training, really. So, I have all these structures hanging on the corridor; the devices that we make. And they're quite complex. They're very small. They are on the sub-micron size.
But I think that when we measure and we get some interesting result, people are interested. They look at it. It’s interesting. And when we ask them, “Why don’t you also do this stuff?” or so, I hear back “Oh, no, no, we are behind you by light years. We'll do something else.” So, it’s just a niche that I found not by running away from another niche; it’s just that I found this niche that there is plenty to do, and very few are doing it. So, the plan, when I wrote my research proposal coming to Weizmann, was very, very different from the actual work that I really did. Because it evolved very quickly and students gave ideas, and theorists gave other ideas. I'm strongly connected with the theorists in the department. We talk a lot. You go to look for something. You find something else at all- serendipity. Today, the Department of Physics changed a lot. The group of doing mostly optics flourished, and so the astrophysics group. These changes are credited Haim Harari, who took a chance with allowing the construction of the sub-micron center. Investing money on top of a debt Weizmann had. So, he somehow refinanced the debt that we had, and gave me fifteen and a half million. Now people build centers of $200 million or so. But this was okay at that time, and now we are expanding the center. But at the time, this was a very smart decision that he did, because he could have said, “Forget it. No.” So I would go—or to the Technion or to some other place. So, I think that I was privileged to suffer during the process of building such a big place. At the same time to see the fruits of it.
Were you thinking about mesoscopic materials from the very beginning?
Yeah. Of course. So, since I knew, and I grew with my own hands, material growth, MBE system, molecular beam epitaxy system, I bought two MBE systems. And I trained people, and now we have here one of the best gallium arsenide material in the world grown now by Vladimir Umansky. Nano-wires are grown by my postdoc in IBM that came back with me, Hadas Shtrikman. I always preach that the material quality is the most important part of any experiment. If you start with crap, you get crap. You have to get the best possible material, so if you have an effect, you see a peak, or a valley, or something happen, you know it’s real. If, on the other hand, the material is just not very good, as in many places in the world, disorder may affect the observable effects. And then later on, after years, when the material is very clean. you can start believing in the data. And I thought that one of the important decision is to have here our own material. If you look at Harvard, they don’t grow their own material. If you look at MIT, they don’t grow their own material. They get it from somebody else. I insisted that we should have our own epitaxially grown material here. And I think then, I would not be dependent on anybody. I don’t need any favors.
I wonder if you can explain your motivations in developing novel electronic interferometers to, quote unquote, “turn on and off electrons.”
Yeah, I never thought about this, in this respect. But if you create a destructive interference between two paths, nothing comes out? So, you could say, “Ah, what do you mean, nothing comes out” Where are the electrons? They are fully reflected! There’s conservation. They cannot disappear. They're not photons. Photon can disappear. Electrons cannot. So, you could in a way change the phase and make it switch. My idea was differently. I wanted now, in this interferometer, to put a little box- a little box with electrons and understand how electrons could go through, interact with the box of electrons, and what is the phase they gain by going through the box? You can measure always the conductance, the resistance of the box, and say, “Ah, okay, the resistance is this and this and this.” It has some probability there that you will collide, and there’s a resistance. But I wanted to see not only the transmission, but I want to see the transmission phase. So, this drove me to construct an interferometer and put in one of its patha quantum-dot. And I can measure there the phase evolution of the electrons going through this quantum dot, which is like an artificial atom. So, my idea, after I came here and thought about just building interferometer, was to do this. And my very first student, when I joined, was Amir Yacoby, now in Harvard. Amir Yacoby is now one of the best younger scientists in this field now worldwide in our field A theorist, Joe Imry, supported by arrival at Weizmann. Joe Imry was the most famous theoretical physicist in condensed matter in Israel. I think he coined the name mesoscopic physics. He knew me from IBM, during his sabbaticals.
What were some of the original interests that you had in the quantum Hall effect regime, and how have they changed over the years?
So, the first one was this fractional charge, to measure the fractional charge. And after we measure the fractional charge, then there were ideas that instead of only currents going on the edge, there are also some heat waves. And these heat waves, you don’t see, when you measure conductance or resistance. So, they are called neutral modes. So, we start looking for these neutral modes, and there was a race to find for these neutral modes. So, this was the second thing that popped up. And then, the interferometers that existed at the time were very simple. Fabry-Perot, made of two mirrors. Electrons go back and forth, like a tied string, with a standing wave. And together with my student, we invented the new interferometer, which is used in optics, the Mach-Zehnder interferometer. The Mach Zehnder interferometer interferes only two paths of electrons (and not multiple paths as in the Fabry-Perot interferometer). So, we use it in the quantum Hall effect to interfere electrons in edge modes. It opened up many possibilities of experiments that we are working now.
On the way to study quantum states, we developed a new interferometer. We started to look fractional charges, which are not fermions and not bosons. They have different statistic. Just to remind you, if you take two bosons (ie., photons), and flip them around, the wave function remains the same. If you take two fermions (ie., electrons, and flip them around, wave function gets a minus sign. So, you need to flip them again to get back to the initial state. In the fractional regime, fractional charges have to be flipped a few times to return to the initial state. And this affects a lot the properties of this quantum state. Then there are new states being studied, that when you flip them around, you don’t change the phase, but you go to a totally different wave-function. It’s like in 3D space, you go to a different vector in space. All this large variety of states exist in the quantum Hall effect. You change the magnetic field, you change the density of the electrons, and you move from one state to the other.
However, to prove that they have these fantastic properties, it’s very difficult. You cannot just measure resistance, conductance, and see. You have to build interferometers. You have to measure now how they carry heat and not only carry charge. Because carrying heat reveal new information, we developed in the last few years, how to measure not charge conductance but thermal conductance, which is much more difficult to measure. You need to create a temperature gradient and measure the energy flow from hot to cold. So, you see that now the toolbox that I have here with my group is quite wide. Because we can measure noise fluctuation. We can build interferometers to measure interference. We can measure heat wave moving. Measure thermal transport. And that’s what my group is doing now. In most of the work that we carry now, we’re still use high purity gallium arsenide, which Vladimir grow here in our molecular beam epitaxy system. This keeps me young, in a way (laughter). Competing with students (laughter).
Moty, what has been some of your group’s major accomplishments in dephasing quasi-particles?
Okay, so what I say, these quasiparticles that I'm talking about, these are the states I'm talking about. The last major achievement was to measuring the properties of the state, to prove this non-abelian nature. The quantum state is numbered two and a half. To prove that this state is non-abelian, we measured the state’s thermal properties. This is the work that we are concentrated a lot now. We are also the only ones, as far as I know, that are making these measurements. So, after we determine the nature of this state, it seems to be different from the expected theoretical prediction. In following works we reestablished our findings. I always had a small group. It’s not like in the U.S. that there are forty people or so. I have about eight people. If a larger group, I wouldn't be able to follow what they are doing at all. And this is for me okay. So, if I am allowed to work for a few more years, I will be happy, as still have plenty of work to do.
Moty, at what point did you realize from the beginning of your building this program through all of the difficulties, your body as The Giving Tree, to the awards that you've been recognized with later on—at what point during this transformation did you realize that you had something successful, that you had built something that was durable, that was doing good science?
I never thought about prizes. Didn't cross my mind at all. I just wanted to pursue ideas in the lab., and I just enjoyed it a lot. The point is, it’s not simple. It’s like you go in the desert, and then you see an oasis, and you put your legs in the water, and then you keep going, again, until the next oasis. The work here fails most times, and then a “delta function” in the output makes one walk on water. But when we start getting results, published in nice magazines, being invited to give talks, then you know that you are already, I don’t know, semi-established. I carry with me, all my life, a lot of insecurities. All the way as I told you from home. From my home, from my growing up.
And also being an electrical engineer and coming now to physics, and possibly not knowing everything that they do here. So, what made me somehow survive these insecurities is somehow that I am successful sometimes to have the right gut feeling. So always trying to understand, instead of looking at the formula, what is the electron doing when it is gliding inside there? I'm just putting myself inside there, and I say, “What are you doing?” Okay? And I torture the theorists to tell me something, not only the equation, but tell me something more that I can feel more. And if you have, in general, this feeling of what’s going on, then sometimes you get an idea suddenly. Just few months ago, I was just awake at night. Suddenly, I got this idea. Why don’t we do it? Of course, I didn't sleep all night. And then I talked to theorists, and for the last few months, they are working on it. And I find gold treasure if I actually do the experiment. When you have this spark, this idea comes up, it’s very elating. So, you asked me when did I feel successful? I think the first award that I got, this award in Israel, and I was chosen for Israeli Academy of Science, then you know that you somehow did something. So, there was a couple of Israeli prizes. Because it’s very nice and very fun and so. But I'll tell you that the last one that I got, this Buckley, I never thought there was a chance in the world. This just blew me off. Because I didn't expect it at all. Because it is- I don’t know if you know- well, you know about the Prize, right?
First of all, it’s given to Americans almost exclusively, or work done in the U.S. All the work I did, I- okay, I'm a citizen. I was in U.S. for seventeen years. And the head of the committee that awarded the prize invited me to give a talk two months ago or something like this, in Ohio State University. So, ten minutes before I gave this Zoom talk, she was just chatting with me. And I said, “Look, this is crazy. I didn't expect it.” And she said very nice words. She said there was no even doubt about it. It was so obvious, or something like this. Also, when I taped my thanks- there was taping of thanks that appears on the site, I was very, very emotional about it. And then remember again my parents, and my mother. So, this one is- I never thought that I could reach this point. And why? Because you could see- I could see the names of people that got it. So, the only- the thing that made the prize what it is are the people that holds this prize.
And the other thing is that what that gave me a lot of pleasure is the relatively new program, it’s called the ERC, the European Research Council. So, I initially didn't know anything about it, but the university encouraged me to apply. So, I was in a way successful in getting all three ERC grants in a row (each for five years). This grant became prestigious and was regarded like a prize. When I start writing the second and the third one, I said, right away at the start, that I failed the previous one. The reason I wrote it was because it was true. And the second thing I put myself as me future reviewer. I don’t like to use too often “novel,” “for the first time,” “incredible,” etc. Not blowing my born. So, I was at the Technion in an unrelated committee, it was giving prizes, and one of the professors in the Technion was on my committee of the third proposal of ERC. And he came and told me, “Congratulations on the prize.” “How come you know?” “I was on the committee.” And what he said is, “We like to know the truth.” I told them, “Look, I wrote it when I was already seventy, and thought, you will give it to younger ones.” Anyhow, so I felt accomplished that I thought- I look back at my papers, and said, “Well, it’s not bad at all. There’s this and this and this and this.” But even today when I see it, I feel very, very, you know, I think that when I got the honor, the prize, the Buckley Prize, the twenty-fourth of March or something, so the department made a little thing on the grass outside here. And they asked me to speak. And I said that I came here being scared and I'm still scared. Okay? Because at some point, it might stop, and this confidence that I lack all the time has carried me all my life. And maybe this is what maybe the driving force. Maybe.
Moty, for the last part of our talk, I’d like to ask a few sort of general retrospective questions, and then we'll end looking to the future. So, the first is, because of the interdisciplinary nature of your research, I wonder if you might reflect about what are some related disciplines in physics, in electrical engineering, in mesoscopic physics, that have most benefited your research? And conversely, where do you see other fields being most benefited by your research?
I think that if I am allowed to use this word, what I think I'm known in doing is in a way the ingenuity of the devices, the complexity of the devices, that people may be reluctant to build. And I think that lately people maybe are less afraid to make devices with many layers of fabrication and things like this, because they see- after you do it, and the see the beautiful data coming out. I think my style of doing these things, a mixture of engineering and physics, is something that is not very common. Most people looking for easy measurements. Indeed, every experiment we do takes months and months to reach publication or fail. There’s nothing that you can finish in two weeks of work. So, it takes a long time, so the list of publications is not large. But I think that somehow my group(s) is recognized without many publications. This is work that is very slow, and with many trials and failures. I think that if people know the way we work here, the way my group works, they can see that it’s extremely thorough. And it takes time.
The students sometimes are very disappointed when they have to progress faster, as time goes by. How does it affect other fields? I don’t know if it affects other fields. I think it has a very nice niche in mesoscopic physics. Today there is a slew of many new materials, graphene, and exfoliated materials. And the previous Buckley Prize was on twisting of two layers of graphene, done first in MIT. So, there is now large number of possible new materials. And I'm still working mostly with gallium arsenide. The same material. Because this is sort of like the bible. Clean, and beautiful, and I know what I get. And out of it, I make all kind of other stuff. So, I think my students maybe are in a way affected by this. The students even that continue later. And I hope they will continue.
What is the most satisfying eureka or aha moment in your research career? Something that you didn't understand and then something clicked for you, and it was really emotionally and intellectually satisfying for you?
It happens many times when sometimes I have new idea to do something interesting. But when we make a measurement, say we measured the fractional charge. The first one was a third of the electron charge. The community expects us to measure another fraction, say, a fifth of the electron charge. When we got it too, we walk above ground. And also now this thermal measurements, with the predictions that nearly all states will have a similar universal value, named Kappa. Yet, this particular state, which is very special, having a quasi-particle called Majorana, is expected to have a fractional (half) kappa. And when we studied the suspected state (the 5/2 state), and we get half kappa- we are again floating above ground. We measured half kappa! That’s—I can’t explain you, but the elation is huge. And then you do it again and again, to be sure. You change the temperature. You change the magnetic field. You use another sample. And after you do it so many times and it’s there, you know it’s there. So sometimes, I have such epiphanies once in a while- a few months ago, at night, I got an idea to try something which was not done before. I couldn't sleep. Next morning, talked to Yuval Gefen, who is a collaborator of mine. “What do you think of it? Can we do it?” He said, “Let me see. I don’t know if it’s important. Let me calculate. Let me think about.” So, this is one thing, a new idea. The other thing is measuring and finding something which is just beautiful. Just beautiful. So, this gives me a huge amount of satisfaction.
Moty, the opposite of a eureka moment is those research questions that no matter how hard you try, answers are just impossible. What are those issues that you've done research on where you keep hitting a wall, or where theory provides no guidance, or where the available technology or instrumentation doesn't allow you to do what you want to do? What are some of those issues that stand out in your memory?
As example, we build interferometers, where we want to see interference of fractional charges. Well, somebody already did it recently in Purdue. We never are successful to get interference of fractional charge, with data we trust. And then, we realized that there are these heat wave, this neutral modes I told you, that are just floating around there, all the time, and they dephase the system. They kill the interference. So now, I understand why I don’t see reliable interference of fractional charges, even though I try to do it for years. So now, let’s try to find a way to suppress these heat waves. And then we might be able to see reliable interference. So, this is a continuous frustration of not observing interference of fractional charge.
Do you see your research long term contributing to the effort to create true quantum computers?
I don’t know. I think that everything that we do, we in some fashion do it, but I don’t think about quantum computers at all. This particular five-half state, with kappa equal to half, is predicted to be a very special state that one can do with topological quantum computation. But it is a very fragile state, being visible at very low temperature. Okay, so now we show that this state is a different member of the family of non-abelian states from the one predicted theoretically. I believe we proved that there is a Majorana in this five-half state. Proving Majorana in the edge of nano-wires is not simple. Our recent results (some to be published) will be the last nail in the coffin for the predicted states, though it may depend on the material used. So, there are things that I probably won’t achieve, and maybe a few of them I will achieve. And I think as time goes by, maybe I'll mellow down a little bit. Maybe I'll be more at home (laughter). I'm sure my wife would enjoy it more (laughter).
Moty, that’s perfect. That gets me to my last question. Looking to the future, for however long that you want to remain active, for however long that your wife will let you be as active as you are, what do you want to accomplish personally, and where do you hope to see the field that you've helped to build, where do you want to see the field headed long-term?
I think that in the field now long term is new materials. This gallium arsenide that I use to study basic properties provided an excellent benchmark. The new materials will change the world. They’re called topological materials. People are exfoliating monolayers from materials A or B or C or D. Now they start twisting one with respect to the another. So, the number of materials that people are now inventing or creating is large and growing. The properties of each combination has to be calculated. And now they find out that they take two of them and they twist a little bit- this was the previous Buckley Prize- they become a superconductor. This unexpected behavior may allow understanding of another high temperature superconductor, which is still not understood. So, I think this exciting future in material research is not the type of work that I'm doing. The future will be new materials, with many exotic effects, that can be used- that will be applied to many, many things. I'm sure that in twenty, thirty years from now, all this condensed matter, solid state physics will be very different. My past PhD student who is now in Harvard is coming back by the end of the year. He will bring from Harvard this technology, and I try to educate myself also, to possibly collaborate on some work with such exfoliated materials.
Moty, it has been a great pleasure spending this time with you. I'm so glad that Daniel Zajfman encouraged me to reach out to you, and it has been a real honor to do this. So, thank you so much.
Thank you for spending the time.