QUANTUM LIMIT MAGNETOCONDUCTIVITY IN THE DILUTE IMPURITY REGIME

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Date
1980-03
Authors
ELEGBA, SHAMSI-DEEN BABATUNDE
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Abstract
Shamsi-Deen Babatunde Elegba for the degree of Doctor of Philosophy in the Department of Physics to be taken March 1980 Title: Quantum Limit Magnetoconductivity in the Dilute Impurity RegimeSemiclassical calculation shows that in the limit of high magnetic fields, the Hall conductivity is independent of any scattering mechanism (for closed orbits of the carriers). That this result is not true quantum mechanically for impurity scattering was recently shown by Nozieres and collaborators. However, these workers used an oversimplified model for the impurity scattering and their calculation contains some logical inconsistencies. In the present work, a system containing a low concentration of impurities with short-ranged potentials in the presence of a very strong magnetic field is investigated. Here, fairly realistic potential models, such as the Thomas-Fermi potential are considered. These potential models are approximated in a systematic fashion to obtain a potential model for which there is an exact expression for the single-site t-matrix. The single-site t-matrix is then inserted into a general expression for the static magnetoconductivity tensor. The potential models used are all non-local and their non-locality alters the velocity operator which in turn changes the transport properties of the system. This aspect of the theory is very important and is correctly taken care of in this work. A generalization of the Nozieres result is obtained for the Hall conductivity oxy plus a correction term which is very important in the case of strong potential scattering. Thus the Hall conductivity obtained in this work can differ greatly from the usual semiclassical expression for strong scattering. The result obtained for oxx in the present work is, however, similar to Nozieres' except that the inconsistency in the potential model leads to a different numerical result.
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A DISSERTATION Presented to the Department of Physics and the Graduate School of the University of Oregon in partial fulfillment of the requirements for the degree of Doctor of Philosophy
Keywords
QUANTUM LIMIT,, MAGNETOCONDUCTIVITY,, DILUTE IMPURITY REGIME,
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