Physics of Non-Fermi Liquid Metals

William Marsh Rice University, Houston TX

Investigators

Abstract

This award supports theoretical research on non-Fermi liquid physics in strongly correlated electron systems. There are by now a large number of materials - including high temperature superconductors, heavy fermions, Si-MOSFET's with dilute electrons, quantum dots, and carbon nanotubes - in which electron-electron interactions play a dominant role. The correlated electron community has come to terms with the notion that interactions can lead to a breakdown of Fermi liquid theory. What remains poorly understood is how! The subject is still in its early stage of development, so it is important to try to gain intuitions through paradigmatic systems which are amenable to controlled theoretical approaches. It is also particularly advantageous to address problems for which systematic experiments are possible. With these considerations in mind, the following three projects will be undertaken. Quantum critical heavy fermions: Quantum criticality has broad relevance to a variety of strongly correlated systems. We will focus on heavy fermion metals, in which magnetic quantum critical points have been explicitly identified and a rich set of phenomenology is emerging. We have recently analyzed their critical dynamics, through a theoretical picture (local quantum criticality) in which a destruction of the Kondo effect occurs at the onset of magnetism. Here, we propose to carry out systematic studies on the non-Fermi liquid electronic properties. The issues to be addressed include the single-electron spectrum, Hall effect vs. Fermi surface evolution and fluctuations, possible pseudo-gap behavior due to orthogonality effects, the critical field theory, and quantum phase transitions involving a spiral magnetic order. Interaction and disorder in the two-dimensional electron gas: The most pressing question on the electrons in Si-MOSFET's and related structures is whether a metallic state can occur when interactions are taken into account in a disordered two-dimensional electron gas. We will aim to shed some light on this issue by developing a formalism for the electronic transport, which incorporates the effect of singularities associated with the Coulomb pseudo-gap of the disordered electrons. Magnetic quantum dots as a realization of the quantum critical Bose-Fermi Kondo model: We will study the electronic transport of a model system appropriate for a quantum dot coupled to ferromagnetic metal leads. This system can serve as a realization of the Bose-Fermi Kondo model, and the non-Fermi liquid behavior near its quantum critical point. These projects will contribute to the broad effects to understand electronic materials by the condensed matter community. The theory and theoretical methods are of fundamental interest, and the materials are of technological interest. The work will involve graduate students and postdoctoral fellows, providing opportunities to train the next generation of scientists. Some of the research will be incorporated into the PI's teaching in a classroom setting. Finally, the PI will engage undergraduates from Rice University and REU students sponsored by the Rice Quantum Institute in his research. %%% This grant supports theoretical research on strongly correlated electron systems. Materials exhibiting this behavior, where the electrons in the materials interact strongly, have many novel and unexplained properties. Research into these materials is at the very heart of modern condensed matter physics. Yet, these same materials hold great promise in technological applications. The work will involve graduate students and postdoctoral fellows, providing opportunities to train the next generation of scientists. Some of the research will be incorporated into the PI's teaching in a classroom setting. Finally, the PI will engage undergraduates from Rice University and REU students sponsored by the Rice Quantum Institute in his research. ***