Novel Electronic Phases in Two Dimensions

California Institute Of Technology, Pasadena CA

Investigators

Abstract

This individual investigator award will support experimental condensed matter physics research aimed at the study of the numerous strongly correlated phases that are exhibited by two-dimensional electron systems in semiconductor heterostructures. This field of science has shown remarkable vitality in recent years, with a number of very striking discoveries. For example, a system formed of two parallel two-dimensional electron gases can condense into an exotic superfluid state if the two layers are close enough together. This "excitonic Bose condensate" will be a focus of the project. An important question to be answered is whether this semiconductor system can exhibit the Josephson effect familiar from superconductivity. A second dramatic example of the unusual properties of low dimensional semiconductor systems is the recent discovery of ferromagnetism in certain manganese-doped compounds. Experiments designed to elucidate the basic physical properties of Mn-doped II-VI semiconductor (e.g. ZnCdSe) quantum wells will be undertaken. In particular, the spin polarization of such systems will be studied using a novel quantum tunneling technique. This research will contribute greatly to the education of graduate and undergraduate students and a postdoctoral associate. They will learn skills that prepare them for academic, industrial, or government research careers. This individual investigator award will support a project at the frontier of basic research on advanced semiconductor materials. The aim of this research is to improve the understanding of how large collections of electrons behave. The topics of greatest interest are those in which such collective behavior cannot be directly inferred from the detailed understanding of the properties of individual electrons that now exists. The phenomenon of superconductivity in certain materials is perhaps the best-known example of such an "emergent" phenomenon, but there are many others. The work supported here will concentrate on examples of emergent phenomena in so-called "two-dimensional" electron systems in semiconductors. A particularly interesting example, in which two parallel layers of electrons interact to form a remarkable new collective phase of matter, will be a main focus of this project. In addition, the properties of magnetic semiconductors will form another focus. There is intense interest in such materials stemming from a vision of an advanced new technology called spintronics. Much of the research will be executed by graduate and undergraduate students and a postgraduate associate. Thus this project has a strong educational component and will prepare these young scientists for sophisticated jobs within the Nation's technological base.