Giant Thermoelectric Response of Fluxons in Superconductors

TL;DR

This paper predicts a giant thermoelectric response in superconductors with fluxons, enabling efficient thermoelectric devices at sub-Kelvin temperatures through quantum vortex states.

Contribution

It introduces a novel quantum thermoelectric effect in superconducting vortices, demonstrating giant thermoelectric response using fluxons in type-II superconductors.

Findings

Thermovoltage of a few mV/K predicted at sub-Kelvin temperatures.

ZT value around 1 for SIN junction, exceeding 3 for STM junction.

Potential applications as thermocouple, diode, or bolometer for low-energy photon detection.

Abstract

Thermoelectric devices that operate on quantum principles have been under extensive investigation in the past decades. These devices are at the fundamental limits of miniaturized heat engines and refrigerators, advancing the field of quantum thermodynamics. Most research in this area concerns the use of conduction electrons and holes as charge and heat carriers, and only very recently have superconductors been considered as thermal engines and thermoelectric devices. Here, we investigate the thermoelectric response of an Abrikosov vortex in type-II superconductors in the deep quantum limit. We consider two thermoelectric geometries, a type-II SIN junction and a local Scanning Tunneling Microscope (STM)-tip normal metal probe over the superconductor. We exploit the strong breaking of particle-hole symmetry in bound states at sub-gap energies within the superconducting vortex to realize a giant thermoelectric response in the presence of fluxons. We predict a thermovoltage of a few mV/K at sub-Kelvin temperatures using both semi-analytic and numerical self-consistent solutions of the Bogoliubov-de Gennes equations. Relevant thermoelectric coefficients and figures of merit are found within our model, both in linear and nonlinear regimes. The ZT of the SIN junction is around 1, rising to above 3 for the STM junction centered at the vortex core. We also discuss how this system can be used as a sensitive thermocouple, diode, or localized bolometer to detect low-energy single photons.