Proposal for a phase-coherent thermoelectric transistor

TL;DR

This paper proposes a superconducting thermoelectric transistor capable of high efficiency and large Seebeck coefficients at sub-Kelvin temperatures, with phase-tunable control via magnetic flux, advancing low-temperature thermal management technologies.

Contribution

It introduces a novel phase-coherent superconducting thermoelectric transistor with unprecedented figures of merit and tunable thermoelectric response, combining superconductivity, ferromagnetic insulators, and magnetic flux control.

Findings

Figures of merit up to ~45 achieved

Seebeck coefficients of a few mV/K demonstrated

Device efficiency approaches Carnot limit

Abstract

Identifying materials and devices which offer efficient thermoelectric effects at low temperature is a major obstacle for the development of thermal management strategies for low-temperature electronic systems. Superconductors cannot offer a solution since their near perfect electron-hole symmetry leads to a negligible thermoelectric response; however, here we demonstrate theoretically a superconducting thermoelectric transistor which offers unparalleled figures of merit of up to $\sim 45$ and Seebeck coefficients as large as a few mV/K at sub-Kelvin temperatures. The device is also phase-tunable meaning its thermoelectric response for power generation can be precisely controlled with a small magnetic field. Our concept is based on a superconductor-normal metal-superconductor interferometer in which the normal metal weak-link is tunnel coupled to a ferromagnetic insulator and a Zeeman split superconductor. Upon application of an external magnetic flux, the interferometer enables phase-coherent manipulation of thermoelectric properties whilst offering efficiencies which approach the Carnot limit.