Polarized heat current generated by quantum pumping in two-dimensional topological insulators

TL;DR

This paper investigates how quantum pumping in a two-dimensional topological insulator with a double quantum point contact can generate polarized heat currents, influenced by electron interactions and external gate modulation.

Contribution

It introduces a microscopic model for quantum pumping in topological insulators and analyzes the polarization of heat currents, highlighting the effects of electron interactions.

Findings

Heat flow is associated with a single spin component due to helical edge states.

Electron-electron interactions reduce the polarization of heat currents.

Separate control of heat and charge flows is possible by adjusting the external gate amplitude.

Abstract

We consider transport properties of a two dimensional topological insulator in a double quantum point contact geometry in presence of a time-dependent external field. In the proposed setup an external gate is placed above a single constriction and it couples only with electrons belonging to the top edge. This asymmetric configuration and the presence of an ac signal allow for a quantum pumping mechanism, which, in turn, can generate finite heat and charge currents in an unbiased device configuration. A microscopic model for the coupling with the external time-dependent gate potential is developed and the induced finite heat and charge currents are investigated. We demonstrate that in the non-interacting case, heat flow is associated with a single spin component, due to the helical nature of the edge states, and therefore a finite and polarized heat current is obtained in this configuration. The presence of e-e interchannel interactions strongly affects the current signal, lowering the degree of polarization of the system. Finally, we also show that separate heat and charge flows can be achieved, varying the amplitude of the external gate.