Dissertation/Thesis Abstract

Linear and Nonlinear Electromagnetic Responses in Topological Semimetals
by Zhong, Shudan, Ph.D., University of California, Berkeley, 2018, 84; 13421373
Abstract (Summary)

The topological consequences of time reversal symmetry breaking in two dimensional electronic systems have been a focus of interest since the discovery of the quantum Hall effects. Similarly interesting phenomena arise from breaking inversion symmetry in three dimensional systems. For example, in Dirac and Weyl semimetals the inversion symmetry breaking allows for non-trivial topological states that contain symmetry-protected pairs of chiral gapless fermions. This thesis presents our work on the linear and nonlinear electromagnetic responses in topological semimetals using both a semiclassical Boltzmann equation approach and a full quantum mechanical approach. In the linear response, we find a "gyrotropic magnetic effect" (GME) where the current density j B in a clean metal is induced by a slowly-varying magnetic field. It is shown that the experimental implications and microscopic origin of GME are both very different from the chiral magnetic effect (CME). We develop a systematic way to study general nonlinear electromagnetic responses in the low-frequency limit using a Floquet approach and we use it to study the circular photogalvanic effect (CPGE) and second-harmonic generation (SHG). Moreover, we derive a semiclassical formula for magnetoresistance in the weak field regime, which includes both the Berry curvature and the orbital magnetic moment. Our semiclassical result may explain the recent experimental observations on topological semimetals. In the end, we present our work on the Hall conductivity of insulators in a static inhomogeneous electric field and we discuss its relation to Hall viscosity.

Indexing (document details)
Advisor: Moore, Joel E.
Commitee: Lee, Dung-Hai, Zworski, Maciej
School: University of California, Berkeley
Department: Physics
School Location: United States -- California
Source: DAI-B 80/08(E), Dissertation Abstracts International
Subjects: Physics, Condensed matter physics
Keywords: Circular photogalvanic effect, Symmetry-protected pairs, Time reversal symmetry
Publication Number: 13421373
ISBN: 9781392035641
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