Thermodynamic Measurements of Collective Phases of Two-Dimensionally Confined Charge Carriers

Purdue University, West Lafayette IN

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). ***** NON- TECHNICAL ABSTRACT **** The two-dimensional electron gas confined to semiconductor interfaces has been one of the important model systems of contemporary condensed matter physics. When the level of disorder in the host semiconductor is low enough and the randomizing effect of temperature is reduced, the electrons are free to order in a rich variety of interesting phases. Historically, with the continuous improvement of sample quality new electronic phases have been discovered. Some phases are well understood while others are currently under intense investigation. Instead of the more common studies utilizing the dc transport of electrons through the system, this project will use thermodynamic measurements to probe previously inaccessible properties of known electronic phases and yield insight into the nature of the newly discovered, exotic phases. The experiments will employ state-of-the art cryogenic and electronic instruments and modern semiconductor processing. Aside from advancing our fundamental understanding of these intriguing systems, this research could have an impact of future technologies. This project will educate a doctoral student in modern condensed matter physics and training in advanced technologies. Work in such a field is proven to be an excellent preparation for a large spectrum of scientific careers from academia to industry. Undergraduate students will be introduced to concepts and techniques of condensed matter physics. ****TECHNICAL ABSTRACT**** Much of our knowledge of low dimensional fermionic systems comes from studies on two-dimensional electron gases. When subjected to low temperatures and an external magnetic field, these systems exhibit a large number of exotic electronic phases. Some of the phases such as the integer and fractional quantum Hall states and the Wigner solid are well understood. Others such as states with even denominator filling factors are under intense investigation. This project will utilize thermodynamic measurements to explore and elucidate the unusual properties of confined correlated electrons. A new technique will be used which employs the decoupling of the electrons from the phonons in the system at dilution refrigerator temperatures. These measurements will yield new insight into known but not fully understood phases as well as provide information on the most recently discovered states. This project will provide excellent preparation for graduate students for their future academic or industrial careers through the study of modern condensed matter physics and training in modern semiconductor processing, in conducting low level measurements, and in the use of cryogenic equipment. Undergraduate students will be introduced to concepts and techniques of condensed matter physics.