MAGNETOTRANSPORT IN TWO DIMENSIONAL ELECTRON SYSTEMS UNDER MICROWAVE EXCITATION AND IN HIGHLY ORIENTED PYROLYTIC GRAPHITE by

This thesis consists of two parts. The first part considers the effect of microwave radi-ation on magnetotransport in high quality GaAs/AlGaAs heterostructure two dimensional electron systems. The effect of microwave (MW) radiation on electron temperature was stud-ied by investigating the amplitude of the Shubnikov de Haas (SdH) oscillations in a regime where the cyclotron frequency ωc and the MW angular frequency ω satisfy 2ω ≤ ωc ≤ 3.5ω. 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 investi-gated. The results demonstrate the first indications of polarization dependence of MW induced magnetoresistance oscillations. In the second part, experiments on the magneto-transport 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