Anomalous proximity effect of a spin-singlet superconductor with a spin-orbit interaction

TL;DR

This paper reveals that a spin-singlet d-wave superconductor with specific spin-orbit interaction can exhibit an anomalous proximity effect, characterized by quantized zero-bias conductance, even without surface zero-energy states.

Contribution

It demonstrates the anomalous proximity effect in spin-singlet superconductors with spin-orbit interaction, expanding understanding beyond spin-triplet cases.

Findings

Quantization of zero-bias conductance observed

Anomalous proximity effect occurs without surface zero-energy states

Relation to experimental results on CoSi₂/TiSi₂ junction

Abstract

The anomalous proximity effect of a spin-triplet $p$-wave superconductor has been known as a part of the Majorana physics and is explained by the penetration of zero-energy states from a surface of a superconductor to a dirty normal metal. We demonstrate that a spin-singlet $d$-wave superconductor without any surface zero-energy states exhibits the anomalous proximity effect in the presence of a specific spin-orbit interaction. The results show the quantization of the zero-bias conductance in a dirty normal-metal/superconductor junction. We also discuss a relation between our findings and results in an experiment on a CoSi$_2$/TiSi$_2$ junction.