Self-consistent evaluation of proximity and inverse proximity effects with pair-breaking in diffusive SN junctions

TL;DR

This paper models the effects of pair-breaking processes on the density of states in diffusive SN junctions, revealing how they influence zero-bias conductance and comparing results with recent experimental observations.

Contribution

It introduces a self-consistent approach to evaluate proximity and inverse proximity effects with pair-breaking in diffusive SN junctions, including interface transparency effects.

Findings

Pair-breaking fills the superconducting gap at zero energy.

Zero-bias conductance exhibits exponential rise near the junction.

Model aligns with recent experimental data on 4Hb-TaS2.

Abstract

We consider a planar superconducting-normal-metal (SN) junction with both inelastic and spin-flip scattering processes present. In the diffusive limit, we use a one-dimensional formulation of the Usadel equation to compute the self-consistent energy dependence of the single-particle density of states as a function of distance from the interface on both the superconducting and metallic sides for various spatial profiles of a pair-breaking spin-flip term. The pair-breaking processes fill in the superconducting gap at zero energy, which is reflected in the zero-bias tunneling conductance in scanning tunneling microscopy/spectroscopy experiments, in the vicinity of the junction. We also investigate the impact of having a partially transparent interface at the junction. We compare our findings with the observed exponential rise in the zero-bias conductance at the 1H step edge in recent experiments on 4Hb-TaS$_2$ [A. K. Nayak et al., Nat. Phys. 17, 1413 (2021)].