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Magnetotransport in Two Dimensional Electron Systems Under Microwave Excitation and in Highly Oriented Pyrolytic Graphite
GEORGIA STATE UNIV ATLANTA
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This thesis consists of two parts. The first part considers the e effect of microwave radiation on magnetotransport in high quality GaAsAlGaAs heterostructure two dimensional electron systems. The effect of microwave MW radiation on electron temperature was studied by investigating the amplitude of the Shubnikov de Haas SdH oscillations in a regime where the cyclotron frequency omegaC and the MW angular frequency satisfy 2omega omegac 35omega. The results indicate negligible electron heating under modest MW photoexcitation, in agree ment with theoretical predictions. Next, the effect of the polarization direction of the linearly polarized MWs on the MW induced magnetoresistance oscillation amplitude was investigated. The results demonstrate the first indications of polarization dependence of MW induced magnetoresistance oscillations. In the second part, experiments on the magnetotransport of three dimensional highly oriented pyrolytic graphite HOPG reveal a non-zero Berry phase for HOPG. Furthermore, a novel phase relation between oscillatory magneto and Hall- resistances was discovered from the studies of the HOPG specimen.
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