Date of Award
8-2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physics and Astronomy
Committee Chair/Advisor
Dr. Catalina Marinescu
Committee Member
Dr. Chad Sosolik
Committee Member
Dr. Endre Takacs
Committee Member
Dr. Sumanta Tewari
Abstract
In this thesis, we discuss the existence of spin and charge currents in systems with broken spin inversion symmetry proportional to the magnitude square of the driving electric and thermal fields. This outcome is predicated on symmetry considerations in the momentum space, whereby the product between the current operator and the out-of-equilibrium distribution function has to be even.
First, we derive the second-order correction to the particle distribution function $\delta f^{(2)}$ in a semi-classical approximation, considering the local change in the equilibrium distribution function caused by external fields. Our approach departs significantly from the previous theory where $\delta f^{(2)}$ is written as an iterative solution to the Boltzmann transport equation in the relaxation time approximation. As we show, such an expression is not self-consistent. In the case of a quantum well with arbitrary values of the linear Rashba $\alpha$ and Dresselhaus $\beta$ interactions, our formalism obtained analytical results for various spin currents. The magnitude of these currents is smaller than previously anticipated in competing theories.
The same second-order distribution function is used to compute the non-reciprocal charge current that appears in a bulk semiconductor with Rashba spin-orbit coupling subjected to crossed electric and magnetic fields. Based on a different expression of the distribution function, previous calculations found, surprisingly, that the electric current exists only for negative chemical potential values in the equivalent two-dimensional system. The problem of this sharp, non-physical discontinuity is solved here by considering the different distribution function and the chiral dependence of the relaxation times.
Recommended Citation
Pan, Aniruddha, "Nonlinear charge and spin currents in non-centrosymmetric electron systems" (2023). All Dissertations. 3380.
https://tigerprints.clemson.edu/all_dissertations/3380
Author ORCID Identifier
https://orcid.org/0000-0002-2587-5714