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. 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 the most sensitive charge sensor in existence. This powerful transistor will also be used to study magnetic properties of stacked layers of these unusual liquids. In addition to conventional semiconductor structures, the work will expanded to emerging two-dimensional electron systems based on higher bandgap semiconductors. On the educational side, the project will provide excellent training for graduate and undergraduate students. The outreach activities, such as physics demonstrations and public lectures, which typically focus on semiconductors, will benefit participating local high school students.
This project will address some of the 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 (SETs) in an Aharonov-Bohm type interference structure. SETs will also be used to study bulk transport properties in quantum Hall liquids. In particular longitudinal conductivity measurements will be performed in the deep insulating regime where conventional transport measurements are not doable. Persistent eddy currents will be investigated in stacked layers of quantum Hall liquids to test an interesting prediction that such stacked layers can be perfectly diamagnetic at zero temperature. In addition to GaAs/AlGaAs heterostructures, quantum transport properties of emerging two-dimensional electron systems based on higher bandgap semiconductors will be investigated in both gated Hall bar and quantum point contact structures. On the educational side, the project will provide excellent training for graduate and undergraduate students. The outreach activities, such as physics demonstrations and public lectures, which typically focus on semiconductors, will benefit participating local high school students.
