Minigap in a SN junction with paramagnetic impurities

TL;DR

This paper investigates how spin-flip scattering influences the minigap in a long diffusive superconductor-normal metal junction, revealing the critical scattering rate at which the minigap closes, scaled by the Thouless energy.

Contribution

It provides a calculation of the critical spin-flip scattering rate and its dependence on the minigap in a diffusive S-N junction, highlighting the Thouless energy scale.

Findings

The minigap closes at a critical spin-flip rate proportional to the Thouless energy.

The minigap and critical rate are governed by the Thouless energy, not the superconducting gap.

The study quantifies the dependence of the minigap on spin-flip scattering.

Abstract

We study the effect of spin-flip scattering on the density of states in a long diffusive S-N junction with transparent interface. We calculate the critical value of the spin-flip scattering rate at which the minigap closes and give the dependence of the minigap on the spin-flip rate. For the system we consider, the minigap and the critical spin-flip rate have the scale of the Thouless energy, and not of the superconducting gap.