Unidirectional Seebeck effect in magnetic topological insulators

TL;DR

This paper theoretically explores the unidirectional Seebeck effect in magnetic topological insulator heterostructures, revealing its quantum origin, dependence on magnetization orientation, doping type, and temperature, with potential implications for thermoelectric applications.

Contribution

It introduces a quantum-mechanical explanation for the unidirectional Seebeck effect in magnetic topological insulators, highlighting its dependence on magnetization and doping.

Findings

USE exhibits cosφ dependence on magnetization orientation.

Sign of USE remains unchanged from p- to n-doping.

USE shows inverse-linear temperature dependence at high temperatures.

Abstract

We theoretically investigate the temperature gradient-dependent or unidirectional Seebeck effect (USE) in a magnetic/ nonmagnetic topological insulator (TI) heterostructure with in-plane magnetization in terms of the semiclassical electron dynamics and Fermi golden rule. The USE has a quantum origin arising from the magnon asymmetric scattering of surface Dirac electrons on TI. We discuss the USE in the heterostructures, Cr$_{x}$(Bi$_{1-y}$Sb$_y$)$_{2-x}$Te$_{3}$/ (Bi$_{1-y}$Sb$_{y})_2$Te$_{3}$. The USE exhibits $\cos\phi$-dependence (measured from $y$-direction) on the orientation of magnetization. It's found that the sign of USE stays unchanged when the system is transferred from $p$-doping to $n$-doping. The USE shows on inverse-linearly temperature dependent at high temperature.