Focused Crossed Andreev Reflection

TL;DR

This paper investigates how electron focusing using magnetic fields can control the balance between crossed Andreev reflection and electron transfer in a superconductor-normal metal system, enabling non-local signals over large distances.

Contribution

It demonstrates that weak magnetic fields can tune the ratio of CAR to ET and extend non-local signals beyond the superconductor's coherence length.

Findings

Magnetic focusing modulates CAR and ET ratios.

Non-local signals can be observed over distances comparable to the mean free path.

Selective enhancement of CAR or ET by magnetic field tuning.

Abstract

We consider non-local transport in a system with one superconducting and two normal metal terminals. Electron focusing by weak perpendicular magnetic fields is shown to tune the ratio between crossed Andreev reflection (CAR) and electron transfer (ET) in the non-local current response. Additionally, electron focusing facilitates non-local signals between normal metal contacts where the separation is as large as the mean free path rather than being limited by the coherence length of the superconductor. CAR and ET can be selectively enhanced by modulating the magnetic field.