Dissertations, Theses, and Capstone Projects

Date of Degree

2-2017

Document Type

Dissertation

Degree Name

Ph.D.

Program

Physics

Advisor

Sergey Vitkalov

Committee Members

Scott Dietrich

Dmitry Garanin

Javad Shabani

Jiufeng Tu

Subject Categories

Condensed Matter Physics

Keywords

Quantum Well, Magnetoresistance, Transport, Zeeman Effect

Abstract

There exists a myriad of quantum transport phenomena in highly mobile 2D electrons placed in a perpendicular magnetic field. We study the effects of tilted magnetic field on these transport properties to understand how the energy spectrum evolves. We observe significant changes of the electron transport in quantum wells of varying widths with high electron densities at high filling factors. In narrow quantum wells the spin splitting of Landau levels due to Zeeman effect is found to be the dominant mechanism reducing Quantum Positive Magnetoresistance. In wider quantum wells with two populated subbands Magnetointersubband oscillations appear to exhibit effects from both Zeeman splitting and orbital coupling of levels due to parallel field, with the latter effect dominating. For the largest tilt angles these effects eliminate Magnetointersubband resistance oscillations completely. The observed effect of Zeeman splitting suggests scattering between spin split subbands which is unexpected. At large tilt angles the observed quantum transport properties suggest a change in electron dynamics resulting in a loss of quantization. Increasing quantum well width further results in a gap opening between symmetric antisymmetric states in the lower subband leading to effects associated with magnetic breakdown of the gap. In this system electric field induced resistance oscillations due to Landau-Zener transitions are studied. Unexpectedly strong inverted resistance oscillations are observed at fields corresponding to minimal modulation of electron density in the regime of magnetic breakdown of semi-classical orbits.

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