Physics News Update, Number 501

Number 501, September 7, 2000 by Phillip F. Schewe and Ben Stein

CAN ELECTRONS SPLIT UP INTO SMALLER FRAGMENTS? Thousands upon thousands of physics experiments have never suggested that the electron is anything but an indivisible particle. However, physicist Humphrey Maris (Brown University/Ecole Normal Superieure, maris@holley.physics.brown.edu, 401-863-2185) proposes that a split-up of electrons into two or more fragments would best explain decades of puzzling results in liquid helium experiments. In these experiments, conducted most actively in the 1960s and 1970s, one phenomenon is well established: Injecting an electron into liquid helium can cause a tiny bubble (approximately 40 angstroms wide) to form around it. Shining light on such bubbles, researchers expected the electrons to escape and zip out of the helium. Not only did they fail to detect such electrons, but other experimenters observed the creation of charged particles, never successfully identified.

Now, Maris proposes a radical explanation: the light causes the electron to break up into two or more pieces, which he terms "electrinos." Fractional charge carriers have been observed before (Update 335), but those are "quasiparticles" resulting from collective actions of many charged particles. In contrast, the electrinos would result from the breakup of single electrons and act as real particles. This split-up, according to Maris, would arise from the quantum ability of electrons--and all matter--to act in some situations not as particles but as waves. According to his picture, light causes the bubble to oscillate in size. Eventually, the oscillating bubble would splinter into multiple bubbles, each carrying part of the electron wave.

Splitting up electron waves also has been demonstrated before (Update 234), but they ordinarily recombine and get detected as full particles. In Maris's scenario, however, the electron waves split up without recombining; they would be detected as fragments of the original electron. Why would this phenomenon occur in liquid helium and not other systems? Maris says that the low-temperature helium bubbles are distinctive electron boxes that can split up cleanly and evenly into two parts because their superfluid properties minimize damping as they oscillate in response to light.

However, fellow Brown physicist Jan Tauc (401-863-2318) contends that even in this liquid helium environment, a split-up of electrons would be precluded by standard quantum-mechanical effects. (Specifically, entanglement of the multiple electron waves would ultimately ensure the emergence of whole electrons, Tauc says.) But what about the unidentified charged particles? Gary Ihas (U. Florida, 352-392-9244) says that mundane explanations have yet to be ruled out; for example, the charged species may be ions made, in part, from impurities in the helium.

Still, respected liquid helium veteran Peter McClintock (Univ. of Lancaster, 011-44-1524-593073) shares others' views when he says that the theory is "Extremely interesting...the ideas have to be taken seriously." All expect that more experiments will decide the issue. (Maris, Journal of Low Temperature Physics, 1 Aug 2000; Select Articles.)

THE FIRST HIGH-PERFORMANCE ALL-POLYMER INTEGRATED CIRCUITS have been developed by scientists at the Philips Research Laboratories in The Netherlands. Although not yet as fast as silicon circuits, polymer components have the virtue of being lightweight, flexible, and potentially easier to fabricate since the temperatures used are much lower, the substrate can be cheap plastic instead of expensive glass, and in some cases the ICs can be printed instead of etched. This will come in handy for low-end, high-volume microelectronics applications such as identification and product tagging and anti-theft stickers.

The progress reported now by the Philips researchers (Gerwin Gelinck, gerwin.gelinck@philips.com) features a great improvement in carrier speed and processing time by the use of a transistor geometry with gates on the bottom and vertical interconnects ("vias") patterned photochemically in the dielectric insulator layer. (Gelinck et al., Applied Physics Letters, 4 September 2000; Select Articles.) Philips recently announced that it had employed this technology in creating the first active matrix display in which each pixel is driven by an organic transistor.