Wave-packet scattering at a normal-superconductor interface in two-dimensional materials: a generalized theoretical approach

TL;DR

This paper introduces a versatile wave-packet evolution method to analyze quasi-particle scattering at normal-superconductor interfaces, applicable to various two-dimensional materials and revealing detailed Andreev reflection phenomena.

Contribution

A generalized split-operator wave-packet method for studying quasi-particle scattering at arbitrary normal-superconductor interfaces in 2D materials.

Findings

Observation of specular and retro Andreev reflection in graphene.

Analysis of zero-gap channel effects on electron and hole scattering.

Method applicable to diverse 2D materials and quasi-particle types.

Abstract

A wave-packet time evolution method, based on the split-operator technique, is developed to investigate the scattering of quasi-particles at a normal-superconductor interface of arbitrary profile and shape. As a practical application, we consider a system where low energy electrons can be described as Dirac particles, which is the case for most two-dimensional materials, such as graphene and transition metal dichalcogenides. However the method is easily adapted for other cases such as electrons in few layer black phosphorus, or any Schr\"odinger quasi-particles within the effective mass approximation in semiconductors. We employ the method to revisit Andreev reflection in graphene, where specular and retro reflection cases are observed for electrons scattered by a step-like superconducting region. The effect of opening a zero-gap channel across the superconducting region on the electron and hole scattering is also addressed, as an example of the versatility of the technique proposed here.