Dynamical Mean-Field Theory description of the voltage induced transition in a non-equilibrium superconductor

TL;DR

This paper uses dynamical mean-field theory to analyze how voltage bias can induce a transition from superconducting to normal state in a heterostructure, revealing an intermediate bad superconducting phase.

Contribution

It introduces a DMFT-based approach to study non-equilibrium superconductivity under voltage bias, highlighting the transition mechanism and intermediate states.

Findings

Superconductivity is destabilized by voltage biases comparable to the energy gap.

An intermediate bad superconducting state appears during the transition.

The transition involves incoherent excitations and reduced order parameter.

Abstract

Using dynamical mean-field theory (DMFT) we study a simplified model for heterostructures involving superconductors. The system is driven out-of-equilibrium by a voltage bias, imposed as an imbalance of chemical potential at the interface. We solve the self-consistent DMFT equations using iterative second-order perturbation theory in the Nambu-Keldysh formalism. We show that the superconducting state is destabilized by voltage biases of the order of the energy gap. We demonstrate that the transition to the normal state occurs through an intermediate bad superconducting state, which is characterized by a smaller value of the order parameter and incoherent excitations. We discuss the energetic balance behind the stabilization of such exotic superconducting state.