Enhancement of thermoelectric effect in diffusive superconducting bilayers with magnetic interfaces

TL;DR

This paper studies how spin-active interfaces in superconducting bilayers can significantly enhance thermoelectric currents, which are spatially confined near the interface due to impurity scattering effects.

Contribution

It reveals the dual role of spin-sensitive scattering in boosting thermoelectric effects and how impurity scattering limits their spatial extent in superconducting bilayers.

Findings

Thermoelectric currents are enhanced near spin-active interfaces.

Electron-hole imbalance is suppressed by non-magnetic impurity scattering.

Maximum thermoelectric effect occurs when the mean free path matches the bilayer thickness.

Abstract

We demonstrate that thermoelectric currents in superconducting bilayers with a spin-active interface are controlled by the two competing processes. On one hand, spin-sensitive quasiparticle scattering at such interface generates electron-hole imbalance and yields orders-of-magnitude enhancement of the thermoelectric effect in the system. On the other hand, this electron-hole imbalance gets suppressed in the superconductor bulk due to electron scattering on non-magnetic impurities. As a result, large thermoelectric currents can only flow in the vicinity of the spin-active interface and decay away from this interface at a distance exceeding the electron elastic mean free path $\ell$. The magnitude of the thermoelectric effect reaches its maximum provided $\ell$ becomes of order of the total bilayer thickness.