Dissipation-enhanced nonreciprocal superconductivity: Application to multivalley superconductors

The superconducting diode effect, characterized by asymmetrical critical currents in opposite directions, is interesting in terms of both fundamental physics and potential for quantum electronics. This Letter offers a mechanism for the effect, based on a nonequilibrium theoretical framework that goes beyond conventional approaches. This approach allows the authors to incorporate the coupling between dissipative currents and time-reversal-symmetry-breaking order parameters, which can stabilize very strong nonreciprocity. While the mechanism is specifically illustrated for systems with two valleys, such as multilayer graphene, it remains more generally applicable.