Study of Quantum Hall Liquids using Single Electron Transistors

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

******NON-TECHNICAL ABSTRACT****** At high magnetic fields, electrons that are confined to move in two directions form new states of matter known as fractional quantum Hall liquids. In such matter, new particles emerge with very unusual properties. For example, in most conductors electrical current is normally carried by electrons with a well-known charge of e. In superconductors, current is carried by pairs of electrons with a charge of 2e. By contrast, in fractional quantum Hall liquids, current is carried by unusual particles with fractional charge of e/3, e/5, and so on. Since electrons are known to be indivisible, the emergence of such fractionally charged particles has been one most fascinating manifestations of many electron quantum phenomena. This project will study these fascinating new particles using devices called single electron transistors. The single electron transistor can be turned on and off by a single electron, and is thus the most sensitive charge sensor in existence. Using this type of a highly sensitive transistor, magnetic properties of quantum Hall liquids will also be explored. On the educational side, the project will provide excellent training for participating graduate and undergraduate students in semiconductor physics and nanoscience. In addition, an outreach activity will be mounted in collaboration with a local science museum to promote the interest of K-12 students in science and engineering. ******TECHNICAL ABSTRACT****** This project will address some long-standing fundamental problems in two-dimensional electron systems. Excitations of fractional quantum Hall liquids are predicted to carry fractional charge and obey unusual fractional statistics different from those of fermions or bosons. Fractionalization and statistics of quasiparticles will be studied using single electron transistors in an antidot geometry, which will allow the researchers to perform both noise and Aharonov-Bohm type interference experiments. The statistics of the carriers will be addressed by first loading the edge states around the antidot with a controllable amount of charge and then by monitoring the phase change in an interference experiment. The use of single electron transistors to study bulk transport properties in quantum Hall liquids will enable investigations deep in the insulating regime where conventional transport measurements cannot be performed. On the educational side, the project will provide excellent training for participating graduate and undergraduate students in semiconductor physics and nanoscience. In addition, an outreach activity will be mounted in collaboration with a local science museum to promote the interest of K-12 students in science and engineering.