Crossed Andreev reflection and charge imbalance in diffusive NSN structures

TL;DR

This paper develops a microscopic theory for non-local electron transport in diffusive NSN structures, revealing quantum interference effects and charge imbalance phenomena that align with recent experimental findings.

Contribution

It introduces a comprehensive microscopic model for non-local conductance in diffusive NSN structures with arbitrary interface transmissions, highlighting quantum interference effects.

Findings

Strong enhancement of non-local spectral conductance at low energies

Non-local resistance remains smooth and independent of interface parameters at low energies

Peak in non-local resistance at higher temperatures due to charge imbalance and Andreev reflection

Abstract

We formulate a microscopic theory of non-local electron transport in three-terminal diffusive normal-superconducting-normal (NSN) structures with arbitrary interface transmissions. At low energies $\varepsilon$ we predict strong enhancement of non-local spectral conductance $g_{12} \propto 1/\varepsilon$ due to quantum interference of electrons in disordered N-terminals. In contrast, non-local resistance $R_{12}$ remains smooth at small $\varepsilon$ and, furthermore, is found to depend neither on parameters of NS interfaces nor on those of N-terminals. At higher temperatures $R_{12}$ exhibits a peak caused by the trade-off between charge imbalance and Andreev reflection. Our results are in a good agreement with recent experimental observations and can be used for quantitative analysis of future experiments.