Interface Spin-Orbit Coupling in a Non-centrosymmetric Thin-Film Superconductor

TL;DR

This study investigates how interface spin-orbit coupling affects the critical magnetic field in ultra-thin non-centrosymmetric superconducting Be/Au bilayers, revealing significant enhancements and anisotropic susceptibilities.

Contribution

It provides new experimental insights into the effects of interface spin-orbit coupling on critical fields and spin susceptibilities in non-centrosymmetric superconductors.

Findings

Critical field exceeds Clogston limit by an order of magnitude in thin films.

Critical field scales as Hc||/Δ ~ 1/d, indicating spin-orbit energy proportional to Δ/d^2.

ISOC induces large in-plane but small transverse superconducting susceptibilities.

Abstract

We present a detailed study of the effects of interface spin-orbit coupling (ISOC) on the critical field behavior of non-centrosymmetric (NCS), ultra-thin superconducting Be/Au bilayers. Parallel field measurements were made in bilayers with Be thicknesses in the range of 2 - 10 nm and Au coverages of 0.5 nm. Though the Au had no significant effect on the superconducting gap, it produced profound changes in the spin states of the system. In particular, the parallel critical field exceeded the Clogston limit by an order of magnitude in the thinnest films studied. In addition, the parallel critical field unexpectedly scaled as Hc||/\Delta ~ 1/d suggesting that the spin-orbit coupling energy was proportional to Delta/d^2. Tilted field measurements showed that contrary to recent theory, the ISOC induces a large in-plane superconducting susceptibility but only a very small transverse susceptibility.