Stimulated quasiparticles in spin-split superconductors

TL;DR

This paper explores how electromagnetic fields induce and detect spin imbalances in spin-split superconductors, revealing frequency-dependent effects and multistability due to spin-flip scattering.

Contribution

It demonstrates the creation and detection of spin imbalance via ac fields in spin-split superconductors, highlighting the role of frequency and spin-flip scattering in these processes.

Findings

Oscillating fields induce detectable spin imbalance.

Sign and magnitude depend on frequency and pair-breaking effects.

Multistability arises with spin-flip scattering under ac excitation.

Abstract

In superconductors spin-split by an exchange field, thermal effects are coupled to spin transport. We show how an oscillating electromagnetic field in such systems creates spin imbalance, that can be detected with a spin-polarized probe. The sign and magnitude of the probe signal result from a competition between processes converting field induced spin energy imbalance to spin imbalance, dominant at low frequencies, and microwave-driven pair breaking at high frequencies. In the presence of spin-flip scattering, we show that ac excitation also leads to multistabilities in the superconducting state.