Dissipation-enhanced non-reciprocal superconductivity: application to multi-valley superconductors

TL;DR

This paper proposes a theoretical non-equilibrium mechanism for the superconducting diode effect, emphasizing dissipation and symmetry-breaking in multi-valley superconductors like twisted trilayer graphene.

Contribution

It introduces a generalized time-dependent Ginzburg-Landau model capturing dissipation effects to explain the superconducting diode effect in valley-imbalanced systems.

Findings

Critical current asymmetry can reach perfect diode efficiency.

Dissipation and symmetry-breaking induce non-reciprocal superconductivity.

Rich physics from competition of orders and currents.

Abstract

We here propose and study theoretically a non-equilibrium mechanism for the superconducting diode effect, which applies specifically to the case where time-reversal-symmetry -- a prerequisite for the diode effect -- is spontaneously broken by the superconducting electrons themselves. We employ a generalized time-dependent Ginzburg-Landau formalism to capture dissipation effects in the non-equilibrium current-carrying state via phase slips and show that the coupling of the resistive current to the symmetry-breaking order is enough to induce a diode effect. Depending on parameters, the critical current asymmetry can be sizeable, asymptotically reaching a perfect diode efficiency; the competition of symmetry-breaking order, superconducting and resistive currents gives rise to rich physics, such as current-stabilized, non-equilibrium superconducting correlations. Although our mechanism is more general, the findings are particularly relevant to twisted trilayer and rhombohedral tetralayer graphene, where the symmetry-breaking order parameter refers to the imbalance of the two valleys of the systems.