Transport across junctions of a Weyl and a multi-Weyl semimetal

TL;DR

This paper investigates how tunneling conductance in junctions between Weyl and multi-Weyl semimetals becomes independent of barrier parameters in the thin barrier limit, due to topological properties of the materials.

Contribution

It reveals a topologically driven barrier independence in tunneling conductance specific to Weyl and multi-Weyl semimetal junctions, extending understanding beyond conventional 2D topological materials.

Findings

Conductance becomes independent of barrier strength in the thin barrier limit.

Barrier independence linked to change in topological winding number.

Applicable to both NBN and NBS junctions with arbitrary winding numbers.

Abstract

We study transport across junctions of a Weyl and a multi-Weyl semimetal (WSM and a MSM) separated by a region of thickness $d$ which has a barrier potential $U_0$. We show that in the thin barrier limit ($U_0 \to \infty$ and $d \to 0$ with $\chi=U_0 d/(\hbar v_F)$ kept finite, where $v_F$ is velocity of low-energy electrons and $\hbar$ is Planck's constant), the tunneling conductance $G$ across such a junction becomes independent of $\chi$. We demonstrate that such a barrier independence is a consequence of the change in the topological winding number of the Weyl nodes across the junction and point out that it has no analogue in tunneling conductance of either junctions of two-dimensional topological materials (such as graphene or topological insulators) or those made out of WSMs or MSMs with same topological winding numbers. We study this phenomenon both for normal-barrier-normal (NBN) and normal-barrier-superconductor (NBS) junctions involving WSMs and MSMs with arbitrary winding numbers and discuss experiments which can test our theory.