RUI: Novel Transport Properties in Strongly Interacting Electron Systems

The University Corporation, Northridge, Northridge CA

Investigators

Abstract

This award supports fundamental theoretical and computational research and education on strongly interacting electrons confined to two-dimensions in semiconductors. The PIs will study metal-insulator transitions (MITs). It is generally believed that strong electronic correlations are responsible for both the zero-field MIT in 2D semiconductors and the superconductor-insulator transition in high-Tc superconductors, although there has been no consensus on the microscopic mechanism for either transition. A central goal of this research is to explore whether the zero-field MIT for interacting electrons in 2D has an insightful topological description characterized by the Chern number. Quantum Hall stripe phases will be studied using exact diagonalization and the density matrix renormalization group (DMRG method). An objective is to obtain transport properties using the Chern number description of the wavefunctions and the generalized Thouless number method for many body systems. These calculations are aimed to determine if there is a new liquid-crystal-like metallic phase, a smectic phase, at low temperature. These calculations are intended to elucidate the role played by disorder and quantum fluctuations and to give insight into the nature of these strongly correlated electron systems. The PIs will also use a new method based on the topological characterization of the wavefunction, to study novel transport properties of double layer systems of strongly interacting two dimensional electrons in order to better understand Coulomb drag transport, and longitudinal and transverse spin transport in coupled two layer semiconductor systems. Based on transport properties, the phase diagram and the nature of quantum phase transitions in double layer systems will be determined. This award supports educational experiences for students at California State University Northridge and Sam Houston University enabling them to participate in research. %%% This award supports fundamental theoretical and computational research and education on strongly interacting electrons confined to two-dimensions in semiconductors. The PIs will use an innovative theoretical approach combined with computation to carry out research in three areas, where the PIs will explore: 1.) whether electronic correlations can give rise to a phase transition between metallic and insulating states as the amount of disorder is increased; 2.) whether layered semiconductor systems can be combined in such a way that the interactions between electrons between layers can be manipulated to control the transport of spin and charge in three dimensional semiconductor structures; 3.) the effect of disorder on quantum Hall states of electrons confined to two-dimensions in a strong perpendicular magnetic field. Each of these areas involves fundamental challenges to our understanding of electronic states in materials and involves novel phenomena that arise as a consequence of the correlations among electrons that result from strong electron-electron interactions. This work also contributes to the intellectual foundations for new generations of semiconductor devices. This award supports educational experiences for students at California State University Northridge and Sam Houston University enabling them to participate in research. ***