Orbital effect on intrinsic superconducting diode effect

TL;DR

This paper explores how orbital effects influence the intrinsic superconducting diode effect in bilayer superconductors, revealing sign reversals, state crossovers, and oscillations in the SDE due to varying orbital coupling.

Contribution

It demonstrates the significant role of orbital effects in modulating the superconducting diode effect, including sign reversal and stabilization of exotic pairing states.

Findings

Small orbital effects cause sign reversal of critical current nonreciprocity.

Large orbital effects induce a transition to an orbital Fulde-Ferrell-Larkin-Ovchinnikov state.

Field dependence of SDE exhibits multiple oscillations due to orbital effects.

Abstract

Much ink has recently been spilled on nonreciprocal phenomena in superconductors, especially the superconducting diode effect (SDE) characterized by the nonreciprocity of the critical current $\Delta J_c$. Contrary to the fundamental and practical significance of the SDE, the precise underlying mechanism remains unclear. In this paper, we investigate the impact of an orbital effect on the intrinsic SDE in a bilayer superconductor with Rashba spin-orbit coupling and an in-plane magnetic field. We show that a small orbital effect leads to the sign reversal of $\Delta J_c$ and a crossover of the helical superconducting state at a lower magnetic field than the monolayer superconductor. On the other hand, a large orbital effect induces a decoupling transition, stabilizing a finite momentum Cooper pairing state called the orbital Fulde-Ferrell-Larkin-Ovchinnikov state, and results in the drastic change of the SDE. Owing to the orbital effect, the field dependence of the SDE may show oscillations several times. The results shed light on the mechanism of the SDE in atomically-thin multilayer superconductors.