Quantum interference and the spin orbit interaction in mesoscopic normal-superconducting junctions

TL;DR

This paper investigates how spin orbit interaction influences quantum corrections to conductance in mesoscopic normal-superconducting junctions, revealing sensitivity to spin rotation symmetry breaking and effects on reflectionless tunnelling.

Contribution

It introduces a theoretical analysis of quantum interference effects in NS junctions considering spin orbit coupling and magnetic fields, expanding understanding of conductance corrections.

Findings

Quantum correction sensitive to spin rotation symmetry breaking.

Quantum interference involves electrons and holes in closed loops.

Spin orbit interaction affects reflectionless tunnelling phenomena.

Abstract

We calculate the quantum correction to the classical conductance of a disordered mesoscopic normal-superconducting (NS) junction in which the electron spatial and spin degrees of freedom are coupled by an appreciable spin orbit interaction. We use random matrix theory to describe the scattering in the normal part of the junction and consider both quasi-ballistic and diffusive junctions. The dependence of the junction conductance on the Schottky barrier transparency at the NS interface is also considered. We find that the quantum correction is sensitive to the breaking of spin rotation symmetry even when the junction is in a magnetic field and time reversal symmetry is broken. We demonstrate that this sensitivity is due to quantum interference between scattering processes which involve electrons and holes traversing closed loops in the same direction. We explain why such processes are sensitive to the spin orbit interaction but not to a magnetic field. Finally we consider the effect of the spin orbit interaction on the phenomenon of ``reflectionless tunnelling.''