Conductance Characteristics between a Normal Metal and a Superconductor Carrying a Supercurrent

TL;DR

This paper theoretically investigates how a supercurrent in a superconductor affects conductance characteristics at a normal metal-superconductor interface, revealing novel features like a current-induced central peak and a three-humped structure.

Contribution

It introduces a theoretical analysis of conductance modifications caused by supercurrent in normal metal-superconductor junctions, highlighting new features not previously described.

Findings

Supercurrent lowers and broadens coherence peaks.

Zero-bias conductance peak is affected by supercurrent.

Novel central peak and three-humped structure emerge at intermediate barrier strength.

Abstract

The low-temperature conductance (G) characteristics between a normal metal and a clean superconductor (S) carrying a supercurrent $I_s$ parallel to the interface is theoretically investigated. Increasing $I_s$ causes lowering and broadening of (1) coherence peaks of s-wave S, and d-wave S at (100) contact, (2) midgap-states-induced zero-bias conductance peak for d-wave S at (110) contact, and (3) Andreev-reflection-induced enhancement of $G$ within the gap near the metallic-contact limit. Novel features found include a current-induced central peak and a three-humped structure at intermediate barrier strength, etc.