Theory of the Supercurrent Diode Effect in Rashba Superconductors with Arbitrary Disorder.

We calculate the nonreciprocal critical current and quantify the supercurrent diode effect in two-dimensional Rashba superconductors with arbitrary disorder, using the quasiclassical Eilenberger equation. The nonreciprocity is caused by the helical superconducting state, which appears when both inversion and time-reversal symmetries are broken. In the absence of disorder, we find a very strong diode effect, with the nonreciprocity exceeding 40% at optimal temperatures, magnetic fields, and spin-orbit coupling. We establish that the effect persists even in the presence of strong disorder. We show that the sign of the diode effect changes as magnetic field and disorder are increased, reflecting the changes in the nature of the helical state.