Superconducting Klein and anti-Klein tunneling in Weyl junctions

TL;DR

This paper proposes a new Weyl-semimetal-based heterostructure for observing Klein and anti-Klein tunneling, predicting conductance doubling and providing a theoretical guide for experimental detection in 3D chiral NS junctions.

Contribution

It introduces a novel platform for Klein tunneling in Weyl semimetals and develops a theoretical framework to distinguish Klein and anti-Klein tunneling effects.

Findings

Klein tunneling occurs at normal incidence in Weyl NS junctions.

Differential conductance doubling is predicted due to Klein tunneling.

Anti-Klein tunneling appears with double Weyl semimetals.

Abstract

Klein tunneling is an old topic in relativistic quantum physics, and has been observed recently in graphene where massless particles reside. Here, we propose a new heterostructure platform for Klein tunneling to occur, which consists of a Weyl-semimetal-based normal state/superconductor (NS) junction. By developing a Blonder-Tinkham-Klapwijk-like theory, we find that Klein tunneling occurs at normal incidence, which can lead to differential conductance doubling. If the (single) Weyl semimeltals are replaced by double Weyl semimetals, anti-Klein tunneling will take place of Klein tunneling. Our work provides a theoretical guide for the detection of (anti-)Klein tunneling in three-dimensional chiral NS junctions.