Bending-strain effects in conventional superconductors and superconducting junctions

TL;DR

This paper explores how bending strain in conventional superconductors influences spin-polarized and triplet pairings, inducing spin currents and magnetization effects that could impact superconducting spintronics.

Contribution

It introduces the concept that bending strain induces spin-orbit coupling effects leading to novel pairing and spin transport phenomena in superconducting junctions.

Findings

Strain induces spin-polarized and odd-frequency pairings.

Strain can generate a superconducting spin current in SNS junctions.

Strain causes a $0- extpi$-transition in spin current, switching magnetization sign.

Abstract

We consider the effect of bending-strain in thin films of clean, conventional superconductors (S), and the proximity-induced effect of this strain in SN bilayers with a normal metal (N), and SNS junctions with equal curvatures in each superconductor. We find that the effective spin-orbit coupling due to strain in the superconductor induces both spin-polarized and unequal-spin even-frequency p-wave triplet pairings throughout the superconductor. When interfaced with a normal metal, additional odd-frequency pairings are induced, and their magnitudes can be tuned with the strain. In SNS junctions, the strain alone can induce a superconducting spin current in the junction. The spin-polarized current can undergo a $0-\pi$-transition, resulting in an in-plane, strain-induced magnetization that switches sign as a function of the strain. We discuss the underlying physics and its implications for superconducting spintronics.