Superconducting diode effect in Ising superconductors

Abstract

We study the superconducting diode effect (SDE) in an Ising superconductor with broken basal mirror symmetry in a parallel magnetic field. We show that in the presence of a small Rashba spin splitting, $\hat{I}{”}_R$, the dominant Ising spin-orbit coupling ($\hat{I}{”}_I>>\hat{I}{”}_R$) dramatically enhances the SDE efficiency compared to a Rashba superconductor with $\hat{I}{”}_I=0$ and the same $\hat{I}{”}_R$. The suppression of the SDE for $\hat{I}{”}_I=0$ at $\hat{I}{”}_R$ much larger than the critical temperature ($T_c$) is accidental. At $\hat{I}{”}_R<<T_c$, the SDE efficiency is small because, to linear order, $\hat{I}{”}_R$ can be removed by a gauge transformation. These two factors -- the accidental suppression of the SDE at large $\hat{I}{”}_R$ and the systematic suppression at small $\hat{I}{”}_R$ -- are eliminated by Ising spin-orbit coupling. As a result, SDE efficiency is substantially enhanced for $\hat{I}{”}_I>>\hat{I}{”}_R\ne 0$.

8 pages, 4 figures