Phase-coherent thermoelectricity in superconducting hybrids (Brief Review)

TL;DR

This review discusses recent progress in understanding phase-coherent thermoelectric effects in superconducting hybrid structures, highlighting mechanisms of electron-hole symmetry breaking and control of Josephson currents via temperature gradients.

Contribution

It summarizes recent experimental and theoretical advances in phase-coherent thermoelectric phenomena in superconducting hybrids, emphasizing flux dependence and control mechanisms.

Findings

Thermoelectric effects are significantly enhanced by electron-hole symmetry breaking.

Thermopower exhibits periodic flux dependence, sometimes becoming odd or even functions.

Temperature gradients can control and enhance Josephson currents, inducing $ ext{π}$-junction states.

Abstract

We review some recent advances in studies of phase-coherent thermoelectric effects in superconducting hybrid structures such as, e.g., Andreev interferometers. We elucidate a number of mechanisms of electron-hole symmetry breaking in such systems causing dramatic enhancement of thermoelectric effects. We demonstrate that the flux-dependent thermopower exhibits periodic dependence on the applied magnetic flux $\Phi_x$ which in some limits may reduce to either odd or even functions of $\Phi_x$ in accordance with experimental observations. We also show that dc Josephson current in Andreev interferometers can be controlled and enhanced by applying a temperature gradient which may also cause a nontrivial current-phase relation and a transition to a $\pi$-junction state.