Superconducting orbital diode effect in SN bilayers

TL;DR

This paper investigates the superconducting diode effect in SN bilayers under in-plane magnetic fields, revealing how nonideal interfaces can enhance the effect through an analytical study of limiting cases.

Contribution

It provides a theoretical analysis of how finite interface resistance influences the superconducting diode effect, highlighting nonmonotonic dependence and potential enhancement.

Findings

SDE strength depends nonmonotonically on interface resistance for thin bilayers.

Nonideal interfaces can enhance the superconducting diode effect.

Analytical approach applied to limiting cases of weak inhomogeneities.

Abstract

We study the superconducting diode effect (SDE) in a diffusive superconductor - normal metal (SN) bilayer subjected to an in-plane magnetic field. The supercurrent flows along the layers, perpendicular to the field. The SDE, manifested as an asymmetry in the critical (depairing) currents and kinetic inductance for opposite current directions, arises from an orbital mechanism due to the inhomogeneous distribution of the Meissner currents caused by a spatially varying superfluid density. Recently, Levichev et al. [Phys. Rev. B 108, 094517 (2023)] demonstrated the realization of this effect in such a structure, supporting numerical calculations for an ideal interface with an experiment. In this work, we investigate the influence of a nonideal interface with finite resistance on the SDE. Employing an analytical approach, we focus on limiting cases corresponding to weak intralayer inhomogeneities. We find that the strength of the SDE depends nonmonotonically on the interface resistance when the bilayer thickness is small compared to the coherence length. Remarkably, a nonideal interface can enhance the SDE compared to the ideal case.