Title

Electronic and thermal studies of Hubbard clusters and indium oxide based semiconductors: Exact and first principles methods

Date of Completion

January 2010

Keywords

Nanoscience|Physics, Condensed Matter|Physics, Theory

Degree

Ph.D.

Abstract

Electronic and thermal properties of repulsive Hubbard clusters with different topologies were studied using the eigenvalues from exact calculations. Computations which were focused on electron charge and spin pairing instabilities in a multi-parameter phase space, defined by temperature, magnetic field and chemical potential, lead to properties that are similar to correlated, inhomogeneous bulk systems. We have developed a new scheme using charge and spin susceptibilities to find these instabilities and crossovers. Statistical Mechanics techniques were used to investigate the low temperature behavior of these systems. The results provided important insights in to several many body problems in condensed matter physics. In the second part, we studied the effects of point defects including transition metal doping in indium oxide using Density Functional Theory based methods. Interstitial positions, oxygen vacancies and transition metal doping were central to the study. Our interest was to investigate the changes in conductivity, transparency and magnetism with the introduction of these point defects. ^