Microwave-assisted thermoelectricity in SIS' tunnel junctions

TL;DR

This paper explores microwave-assisted thermoelectric effects in asymmetric SIS' tunnel junctions, revealing how photon absorption/emission influences thermoelectricity and enabling millimeter wavelength signal detection.

Contribution

It demonstrates the interplay of photon-assisted tunneling with thermoelectric effects, introducing a novel microwave-assisted thermoelectric mechanism in superconducting junctions.

Findings

Thermoelectricity is supported by photon sidebands at specific bias voltages.

Multiple stable solutions arise from different photon sidebands when a load is connected.

Nonlinear cooling effects are altered by photon-assisted tunneling processes.

Abstract

Asymmetric superconducting tunnel junctions with gaps $\Delta_1>\Delta_2$ have been proven to show a peculiar nonlinear bipolar thermoelectric effect. This arises due to the spontaneous breaking of electron-hole symmetry in the system, and it is maximized at the matching-peak bias $|V|=V_p=(\Delta_1-\Delta_2)/e$. In this paper, we investigate the interplay of photon-assisted tunneling (PAT) and bipolar thermoelectric generation. In particular, we show how thermoelectricity, at the matching peak, is supported by photon absorption/emission processes at the frequency-shifted sidebands $V=\pm V_p+n\hbar\omega$, $n \in \mathbb{Z}$. This represents a sort of microwave-assisted thermoelectricity. We show the existence of multiple stable solutions, being associated with different photon sidebands, when a load is connected to the junction. Finally, we discuss how the nonlinear cooling effects are modified by the PAT. The proposed device can detect millimeter wavelength signals by converting a temperature gradient into a thermoelectric current or voltage.