Crossed Andreev reflection in superconducting graphene spin-valves: Spin-switch effect

TL;DR

This paper demonstrates a spin-switch effect in a graphene superconducting spin-valve, enabling control over quantum transport processes like elastic co-tunneling and crossed Andreev reflection by reversing magnetization, due to graphene's tunable electronic properties.

Contribution

It introduces a novel method to switch between CT and CAR in graphene spin-valves by tuning the Fermi level, a feat not possible in conventional metallic setups.

Findings

Achieved control over CT and CAR processes via magnetization reversal.

Identified the role of graphene's tunable Fermi level in enabling the spin-switch effect.

Demonstrated potential for noise-free quantum transport control in graphene-based devices.

Abstract

We consider the non-local quantum transport properties of a graphene superconducting spin-valve. It is shown that one may create a spin-switch effect between perfect elastic co-tunneling (CT) and perfect crossed Andreev-reflection (CAR) for all bias voltages in the low-energy regime by reversing the magnetization direction in one of the ferromagnetic layers. This opportunity arises due the possibility of tuning the local Fermi-level in graphene to values equivalent to a weak, magnetic exchange splitting, thus reducing the Fermi surface for minority spins to a single point and rendering graphene to be half-metallic. Such an effect is not attainable in a conventional metallic spin-valve setup, where the contributions from CT and CAR tend to cancel each other and noise-measurements are necessary to distinguish these processes.