Microscopic theory of the proximity effect in superconductor-graphene nanostructures

TL;DR

This paper provides a microscopic theoretical analysis of the proximity effect in graphene-superconductor interfaces, exploring how different interface models influence electronic properties like Andreev reflection and local density of states.

Contribution

It introduces two microscopic interface models for superconductor-graphene systems and analyzes their impact on proximity-induced phenomena at the interface.

Findings

Andreev reflection probability depends on interface model

Induced minigap decreases with increasing graphene layer length

Local density of states profiles vary between finite and semi-infinite layers

Abstract

We present a theoretical analysis of the proximity effect at a graphene-superconductor interface. We use a tight-binding model for the electronic states in this system which allows to describe the interface at the microscopic level. Two different interface models are proposed: one in which the superconductor induces a finite pairing in the graphene regions underneath, thus maintaining the honeycomb structure at the interface and one that assumes that the graphene layer is directly coupled to a bulk superconducting electrode. We show that properties like the Andreev reflection probability and its channel decomposition depend critically on the model used to describe the interface. We also study the proximity effect on the local density of states on the graphene. For finite layers we analyze the induced minigap and how it is reduced when the length of the layer increases. Results for the local density of states profiles for finite and semi-infinite layers are presented.