Thermoelectric effects in quantum Hall systems beyond linear response

TL;DR

This paper investigates nonlinear thermoelectric and spin transport effects in quantum Hall systems with antidots and topological insulators, revealing deviations from classical laws and controllable spin currents.

Contribution

It extends the understanding of nonlinear thermoelectric effects and spin current generation in quantum Hall and topological insulator systems beyond linear response.

Findings

Deviations from Wiedemann-Franz law in nonlinear charge transport.

Magnetic-field asymmetric transport coefficients describe Peltier effects beyond linear response.

Spin currents can be tuned by lead polarization, with nonlinear dependence in antiparallel configurations.

Abstract

We consider a quantum Hall system with an antidot acting as an energy dependent scatterer. In the purely charge case, we find deviations from the Wiedemann-Franz law that take place in the nonlinear regime of transport. We also discuss Peltier effects beyond linear response and describe both effects using magnetic-field asymmetric transport coefficients. For the spin case such as that arising along the helical edge states of a two-dimensional topological insulator, we investigate the generation of spin currents as a result of applied voltage and temperature differences in samples attached to ferromagnetic leads. We find that in the parallel configuration the spin current can be tuned with the leads' polarization even in the linear regime of transport. In contrast, for antiparallel magnetizations the spin currents has a strict nonlinear dependence on the applied fields.