Interfacial control of vortex-limited critical current in type II superconductor films

TL;DR

This paper explores how interfacial Rashba spin-orbit coupling influences vortex penetration and critical current in type II superconductor films, suggesting potential for gate-controlled superconducting properties.

Contribution

It introduces a theoretical framework showing that interfacial spin-orbit coupling can modulate and enhance critical currents in superconductor-magnet heterostructures.

Findings

Interfacial spin-orbit coupling significantly alters vortex surface barriers.

Gate voltage can modulate critical currents via interfacial effects.

Enhanced critical currents observed in NbN films are explained by this mechanism.

Abstract

In a small subset of type II superconductor films, the critical current is determined by a weakened Bean-Livingston barrier posed by the film surfaces to vortex penetration into the sample. A film property thus depends sensitively on the surface or interface to an adjacent material. We theoretically investigate the dependence of vortex barrier and critical current in such films on the Rashba spin-orbit coupling at their interfaces with adjacent materials. Considering an interface with a magnetic insulator, we find the spontaneous supercurrent resulting from the exchange field and interfacial spin-orbit coupling to substantially modify the vortex surface barrier, consistent with a previous prediction. Thus, we show that the critical currents in superconductor-magnet heterostructures can be controlled, and even enhanced, via the interfacial spin-orbit coupling. Since the latter can be controlled via a gate voltage, our analysis predicts a class of heterostructures amenable to gate-voltage modulation of superconducting critical currents. It also sheds light on the recently observed gate-voltage enhancement of critical current in NbN superconducting films.