Spin, Charge, and Energy Transport in Semiconductor Nanostructures and Graphene-Like Materials

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

NON-TECHNICAL SUMMARY Recent advances in experimental techniques have opened the way to unprecedentedly accurate studies of charge and spin dynamics in two-dimensional electronic systems, which are formed at the interface between semiconductors, metals, and metal oxides, and in various layered materials. The ability of these materials to transport spin, charge and energy in an efficient and controllable manner makes them promising candidates for the development of new technologies, both in the field of information processing and in that of energy conversion. This project combines theoretical research and accompanying educational and outreach activities that address key issues relating to charge, spin, and energy transport in single- and multi-layered electronic systems. Particular systems which will be investigated include materials such a single-atom-thick form of carbon, known as graphene, and other graphene-like two-dimensional materials composed of transition metal atoms and sulfur. Through careful analytical and computational studies, the PI will examine the interplay between the spin and charge degrees of freedom in these systems, and predict how external fields (e.g. electric, thermal) can be manipulated to bring out novel phenomena that could lead to technological innovations. This project is strategically positioned at the interface between fundamental condensed matter theory, applied physics, and computational materials science, and has potential technological implications in electronics and thermal energy transport. While carrying out this research with the assistance of postdoctoral researchers and external collaborators, the PI will maintain a weekly seminar on "Selected topics in condensed matter theory", in which the graduate students of the Physics Department at the University of Missouri will be introduced to the basic concepts and methods which underlie the execution of the project. The broader significance of the research will be explained to a wider audience through public lectures delivered by the PI. TECHNICAL SUMMARY Recent advances in experimental techniques such as transient grating spectroscopy, magnetopolarimetry, spin noise spectroscopy, and nonlinear optical generation of spin currents open the way to unprecedentedly accurate studies of charge and spin dynamics in two-dimensional electron liquids, which exist at the interfaces between semiconductors, metals, and metal oxides, and in layered materials such as graphene, MoS2, and the surface of topological insulators. The ability of these systems to transport spin, charge and energy in an efficient and controllable manner makes them promising candidates for the development of new technologies, both in the field of information processing and that of energy conversion. This project combines theoretical research and accompanying educational and outreach activities addressing key issues relating to charge, spin, and energy transport in single- and multi-layered electronic systems. At the core of the projected activity lies a set of basic physics problems which will be addressed in parallel or sequentially during a period of three years. These are: 1. Evaluating the microscopic spin-charge response functions for two-dimensional electron liquids in graphene and graphene-like materials, including electron-electron interactions, disorder, spin-orbit couplings, and magnetic fields in suitable approximations; 2. Developing the theory of spin diffusion, thermal conductivity, and viscosity in graphene and graphene-like materials, to the point where the calculations exhibit the crossover between the collisionless (high-frequency) and collision-dominated (hydrodynamic) regimes; 3. Identifying and quantifying novel thermoelectric phenomena for interacting electrons in multi-layer structures; 4. Developing the theory of spin Hall effect and spin-galvanic effects at metallic and oxide interfaces with strong spin-orbit interactions. This project is strategically positioned at the interface between fundamental condensed matter theory, applied physics, and computational materials science, and has potential technological implications in electronics and thermal energy transport. While carrying out this research with the assistance of postdoctoral researchers and external collaborators, the PI will maintain a weekly seminar on "Selected topics in condensed matter theory", in which the graduate students of the Physics Department at the University of Missouri will be introduced to the basic concepts and methods which underlie the execution of the project. The broader significance of the research will be explained to a wider audience through public lectures delivered by the PI.