Non-local transport in normal-metal/superconductor hybrid structures: the role of interference and interaction

TL;DR

This study investigates how interference and interactions influence non-local electron transport in mesoscopic normal-metal/superconductor hybrid structures, revealing phase-coherent effects and the competition between crossed Andreev reflection and elastic cotunneling.

Contribution

It provides experimental evidence of phase-coherent enhancement of non-local conductance and clarifies the roles of interference and interaction effects in such hybrid systems.

Findings

Observation of subgap anomalies in conductance

Sign change in non-local conductance indicating competing processes

Transport enhancement driven by phase coherence

Abstract

We have measured local and non-local conductance of mesoscopic normal-metal/superconductor hybrid structures fabricated by e-beam lithography and shadow evaporation. The sample geometry consists of a superconducting aluminum bar with two normal-metal wires forming tunnel contacts to the aluminum at distances of the order of the superconducting coherence length. We observe subgap anomalies in both local and non-local conductance that quickly decay with magnetic field and temperature. For the non-local conductance both positive and negative signs are found as a function of bias conditions, indicating at a competition of crossed Andreev reflection and elastic cotunneling. Our data suggest that the signals are caused by a phase-coherent enhancement of transport rather than dynamical Coulomb blockade.