Thermodynamic Measurements of Interacting Disordered Quantum Hall Systems

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Jiang 0071969 This research is focused on the thermodynamic measurements of interacting disordered semiconductor heterostructures. The problem of strong correlations, in low-dimensional quantum systems, is made more difficult by the presence of disorder. Particularly, the thermodynamic properties of interacting disordered quantum Hall devices is still poorly understood. A high density GaAs/AlGaAs quantum well structure with two populated subbands as well as a p-type single-heterostructure with highly correlated holes will be used for the investigations. Compressibility will be measured by using a field-penetration technique to probe the internal interaction energy. Magnetization will be measured by a torsional magnetometer to determine the spin polarization at different electronic phases. Various physical regimes will be explored following the "road-maps" obtained from early transport studies. Electrically controlled gates will be used to vary the density, to alter the screening properties, and to change the spatial correlation of the disorder. Contemporary issues, such as the nature of the zero-field 2D metal-insulator transition, its relation to quantum Hall effect, and consequences of Landau level interactions in two-component systems, will be addressed. This project will also provide an excellent training for graduate and undergraduate students in this program for solid state electronics field. In fact, the semiconductor device fabrication and characterization aspects of the work overlaps closely with what is going on right now in semiconductor electronics industry. %%% This project is concentrated on the study of thermal properties of thin-layered semiconductor structures in the presence of both disorder and carrier interaction. Similar structures are currently used for high-speed electronics and opto-electronics technologies. Due to the intricate interplay of disorder and interaction, the properties of these advanced devices are less predictable, and sometimes even appear to be mysterious. The proposed experiments study the thermal properties of several poorly understood quantum electronic phases by using several high-sensitivity measurement techniques. The main objective is to establish a better understanding on the underlying physical principle of these phases and the wealth of effects exhibited. The better understandings can, in turn, provide a basis for designing the next generation of electronics. The concepts obtained from the proposed experiments can be applied to some of the more complex condensed matter systems. The work concerning electron spins could potentially have impact on the development of future quantum information processing systems for quantum computing and quantum communications. This project will also provide an excellent training for graduate and undergraduate students in this program for solid state electronics field. In fact, the semiconductor device fabrication and characterization aspects of the work overlaps closely with what is going on right now in semiconductor electronics industry.