Spin-pumping in superconductor-antiferromagnetic insulator bilayers

TL;DR

This paper theoretically investigates spin pumping in superconductor-antiferromagnetic insulator bilayers, revealing temperature and frequency-dependent enhancements or suppressions of spin current, with implications for experimental detection.

Contribution

It introduces a comprehensive theoretical model considering both scattering channels and interface types, highlighting conditions for spin-current enhancement in superconductor-based bilayers.

Findings

Spin current is enhanced near the superconductor's critical temperature.

Spin-current suppression occurs at temperatures away from critical points.

Lower precession frequencies can facilitate detection of the enhanced spin current.

Abstract

We study theoretically spin pumping in bilayers consisting of superconductors and antiferromagnetic insulators. We consider both compensated and uncompensated interfaces and include both the regular scattering channel and the Umklapp scattering channel. We find that at temperatures close to the critical temperatures and precession frequencies much lower than the gap, the spin-current is enhanced in superconductors as compared to normal metals. Otherwise, the spin-current is suppressed. The relevant precession frequencies where the spin-current in SC/AFI is enhanced compared to NM/AFI is much lower than the typical resonance frequencies of antiferromagnets, which makes the detection of this effect experimentally challenging. A possible solution lies in the shifting of the resonance frequency by a static magnetic field.