WATERLOO, Ont. (Friday, Jan. 13, 2012) – A three-member international team of theoretical physicists, including a University of Waterloo professor, made a notable discovery about the unusual behaviour of electrons, with implications for all of physics. Their findings appear today in Science,
one of the worldâs pre-eminent journals for original, peer-reviewed scientific research.
This work is a significant step in allowing physicists the rare opportunity to study seemingly impossible fractional particles. The research team includes professor Roger G. Melko of the Department of Physics and Astronomy at Waterloo, professor Matthew Hastings of the Department of Physics at Duke University in Durham, N.C. and also of Microsoft Research at the University of California, and lead author Sergei Isakov, a post-doctoral research associate with the Institut fur Theoretische Physik in Zurich, Switzerland. They used the computer power and capacity that Compute Canada’s Ontario-based supercomputing consortium SHARCNET provides to produce a simulation study that uncovered significant information about fractional particles when cooled to near absolute zero.
The researchers successfully created a simulated crystal of quantum material, which had just the right properties to be tuned to an unusual quantum state near absolute zero. When a particle with the fundamental electron charge was placed in that state, the team observed it fractionalize – or split itself – into two separate objects, each with a charge of half an electron. The researchers were then able to measure several values relating to the motion of the fractional particle. These numbers are universal, and so physicists can apply them across other areas of physics.
âWhat we have shown is not just that fractional particles can be created in a computer, but that they can affect universality at a phase transition. That means certainproperties transcend the specifics of the system, in our case the simulatedmaterial,â said Melko. âThese properties will be present in other systems – physical, chemical, biological – that contain the same type of fractional particle. Thus, our work can be used to guide future studies looking for these odd half-electrons across a variety of disciplines.â
Rather than study high-energy systems, the team took advantage of the fact that low-temperature matter can come together to exhibit remarkable collective behaviour as quasiparticles. The motion of these cooperating particles, when viewed from a distance, is essentially indistinguishable from that of a regular, free particle. And, as they demonstrated in this paper, under just the right conditions, these quasiparticles can contain a fraction of the fundamental electron charge.
âThe potential impact of our work is still unknown. The discovery of fractionalization in the quantum Hall effect revolutionized the way we think of matter. It won a Nobel Prize, and we are still building on this success,â said Melko. âUnderstanding these fractional particles could influence our understanding of superconductivity, help us build better electronics, and even play a part in the design of quantum computers in the future.â
The researchersâ article entitled “Universal Signatures of Fractionalized Quantum Critical Points” follows the team’s paper published last fall in the respected journal Nature Physics. That paper, which initially uncovered evidence for the existence of fractional particles in this low-temperature phase of matter was the result of months of collaboration and computer simulation work.