  Nonreciprocal transport phenomena have attracted much attention in modern
condensed matter physics. In the field of superconductivity, the
superconducting diode effect (SDE) has been one of the central topics. Recent
theoretical studies for the SDE in intrinsic mechanism revealed the relation
between the SDE and helical superconductivity, for which experimental
clarification has been awaited. In this work, we establish a microscopic theory
of the intrinsic SDE in disordered systems. We show that the sign reversal of
the nonreciprocal critical current is suppressed under moderate impurity
concentrations. However, even in the moderately disordered region, the SDE
shows a feature signaling the change in the nature of helical
superconductivity. It is also found that the diode quality factor $r$ is
increased by disorders and reaches 20% in the Rashba-Zeeman model.

Superconductivity