Phase Competition and Domain Textures in the Fractional Quantum Hall Effect

Non-Technical Abstract:

This project investigates a fundamental physics phenomenon called fractional quantum Hall effect (FQHE), which is observed in semiconductor multilayer structures. The investigation is performed on unique ultra-high purity semiconductors exposed to high magnetic fields using novel high sensitivity optical technique. This combination of low-disorder semiconductors and novel measurement methods enables detection of extremely small signals of excitation modes that accompany interactions between electrons in these materials. Traditional methods of magneto-transport measurements are insufficient for detecting these excitations that occur in the bulk of these materials. Studies of these low-lying excitations provide important insights on fundamental interactions in electronic systems with subsequent impacts on the development of quantum computation technology. The project provides training in cutting-edge science to graduate and undergraduate students as well as postdoctoral researchers. Outreach activities are planned to attract diverse group including women and minorities.

Technical Abstract:

The work proposed in this project experimentally probes low-lying excitations in the bulk electron fluids of the fractional quantum Hall effect (FQHE) to understand physics of strong electron correlation in topologically protected electron fluids. While much of the correlation physics in the FQHE is understood in terms of composite fermion quasiparticles, more recent theories introduced an internal geometrical degree of freedom that impacts orbital motion in the large magnetic field due to intra-Landau electron Coulomb interactions. These interactions result in novel effects that uniquely manifest on the dispersions of low-lying excitations. The bulk of the FQHE fluids is known to be disordered in which domains of FQHE fluid coexist with domains of other phases of the two-dimensional (2D) electron fluid. Optical methods will be used to identify large domains of FQHE fluid in which the low-lying excitations have momentum dispersions that are like those of a uniform system. The low-lying modes are studied by advanced resonant inelastic light scattering methods developed in the group of the PI. At Landau level filling nu=1/3 the measurements will be focused on identification chiral gravitons of angular momentum L=-2 predicted by geometrical theories. Much of the proposed research efforts will be focused on the FQHE states of the second Landau level that is host to intriguing FQHE states at Landau level filling factors 5/2 and 7/3. In tilted magnetic field emergent nematic phases and their competition with FQHE phases in the bulk will be studied by optical methods.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.