Superconducting diode effect in Ising superconductors

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, ΔR, the dominant Ising spin-orbit coupling (ΔI≫ΔR) dramatically enhances the SDE efficiency compared to a Rashba superconductor with ΔI=0 and the same ΔR. The suppression of the SDE for ΔI=0 at ΔR much larger than the critical temperature (Tc) is accidental. At ΔR≪Tc, the SDE efficiency is small because, to linear order, ΔR can be removed by a gauge transformation. These two factors - the accidental suppression of the SDE at large ΔR and the systematic suppression at small ΔR - are eliminated by Ising spin-orbit coupling. As a result, SDE efficiency is substantially enhanced for ΔI≫ΔR≠0.