Spin-Transfer and Exchange Torques in Ferromagnetic Superconductors

TL;DR

This paper investigates how superconducting correlations affect spin-transfer and exchange torques in ferromagnetic superconductors, revealing novel phase-dependent effects and equilibrium magnetic torques mediated by Andreev states.

Contribution

It introduces a new particle-hole interference torque dependent on the superconducting phase and demonstrates equilibrium exchange torques influenced by phase differences.

Findings

Discovery of a novel torque from particle-hole interference.

Identification of equilibrium exchange torque mediated by Andreev states.

Sensitivity of torques to superconducting phase differences.

Abstract

We consider how superconducting correlations influence spin-transfer torques in ferromagnetic superconductors. It is demonstrated that there is a novel torque arising from particle-hole interference that depends on the U(1) phase associated with the superconducting order parameter. We also show that there is an equilibrium exchange torque between two ferromagnetic superconductors in contact via a normal metal mediated by Andreev states. The latter equilibrium magnetic torque is also sensitive to spin-resolved phase differences in the superconducting order parameters as well as to an externally applied phase difference.