Experimental Investigations of Properties of Electron Systems

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

The goal of the research supported by this individual investigator grant is to increase our understanding of electron physics. The project has two parts. One seeks to understand a surprising and dramatic behavior of electrons: the sign reversal in a measured transport parameter. This reversal, seen for two-dimensional electrons in magnetic fields smaller than one Tesla, was entirely unanticipated, and remains without explanation. Evidence exists that the unusual behavior is directly related to the electron spin, offering the prospect for new advances in important areas of electron physics. The second part will use a new experimental approach to explore two complex and important influences on electrons: disorder and interactions. These influences have long been established as central to electronic properties; yet a full understanding of their roles, particularly when both are present, remains elusive. This project will use drag to directly measure the electron density fluctuations, thereby investigating the interplay between disorder and electron interactions in electron systems. The insight to be gained through this new approach arises from the substantial difference in density fluctuations theoretically established between the disorder dominated and the interaction dominated regimes. The training provided students involved in this research aims toward answering fundamental questions in the physic of technologically important materials, while involving a wide range of state of the art technical methods. Such training is valuable preparation for academic, government, or industrial scientific careers. This individual investigator award supports research involving basic questions about the properties of electronic materials. Two primary research directions will be examined through experiments. One involves the surprising discovery of new behavior in a regime that had been widely regarded as well understood: two-dimensional electrons in small magnetic fields. Evidence that the spin of the electrons is involved increases the prospect for valuable new understanding. The other research direction involves a new experimental approach applied to a longstanding but fundamental issue of electronic materials: the influences of disorder and of the interactions between electrons. These influences are widely recognized as being of central importance to a broad range of behaviors in electronic materials. Our measurements will provide new insights into this important topic. Complimenting the value of the science investigated here is the value of the training provided to students. The experiments themselves are technically challenging, involving low-noise measurement with complex sample requirements, and the use technologically important materials. They push the boundaries of measurement technology, sample preparation, and even sample growth. The basic research explored in this work offers the prospect of strengthening the intellectual underpinnings of a number of important technological areas, from spin based electronics to ultra-small devices, which rely on a broad understanding of electron physics.