Quasiparticle cooling using a Topological insulator-Superconductor hybrid junction

TL;DR

This paper explores the thermoelectric properties of a topological insulator-superconductor hybrid junction, demonstrating efficient quasiparticle cooling driven by Andreev reflection regimes without impurity scattering.

Contribution

It introduces a scattering matrix approach to analyze thermoelectric effects in topological insulator-superconductor junctions, highlighting regimes for optimal cooling performance.

Findings

Cooling power increases with dominant Andreev retro-reflection.

Efficient cooling achieved without impurity scattering at the interface.

Surface states enable thermoelectric control in topological insulator devices.

Abstract

In this work, we investigate the thermoelectric properties of a hybrid junction realised coupling surface states of a three-dimensional topological insulator with a conventional $s$-wave superconductor. We focus on the ballistic devices and study the quasiparticle flow, carrying both electric and thermal currents, adopting a scattering matrix approach based on conventional Blonder-Tinkham-Klapwijk formalism. We calculate the cooling efficiency of the junction as a function of the microscopic parameters of the normal region (i.e. the chemical potential etc.). The cooling power increases when moving from a regime of Andreev specular-reflection to a regime where Andreev retro-reflection dominates. Differently from the case of a conventional N/S interface, we can achieve efficient cooling of the normal region, without including any explicit impurity scattering at the interface, to increase normal reflection.