Publication Date

2019

Document Type

Dissertation/Thesis

First Advisor

Winkler, Roland

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Physics

Abstract

Due to their extraordinary mechanical, and fascinating electronic properties, atomically flat two-dimensional materials are attractive avenues in the search for new and interesting physical phenomena. Symmetry is a powerful tool in studying the dynamics of Bloch electrons in these crystalline solids. Here, using a tight binding description, a systematic scheme is developed to derive the symmetry labels, called irreducible representations (IRs), characterizing the Bloch eigenstates in a crystal, including an extensive discussion on the possibility that these IRs are not always unique. This theory is illustrated using monolayer MoS$_2$ and few-layer graphene as examples. Using this symmetry analysis in conjunction with the theory of invariants, a generic multiband Hamiltonian for monolayer MoS$_2$ is constructed, which incorporates the effects of spin-orbit coupling, strain and external electric and magnetic fields. In a two-band model, and restricting the system to one dimension, the spin-dependent effective Hamiltonian is found to be applicable to other quasi one-dimensional systems, i.e.\ all of these systems can be described by the same Dirac-like Hamiltonian. Hence, spin-dependent observable effects in one of these systems have counterparts in each of the other systems. Effects discussed in more detail include equilibrium spin currents, current-induced spin polarization (Edelstein effect), and spin currents generated via adiabatic spin pumping.

Extent

229 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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