Signature of Fermi arc surface states in Andreev reflection at the WTe$_2$ Weyl semimetal surface

TL;DR

This study provides experimental evidence of Fermi arc surface states in WTe$_2$ Weyl semimetals through distinctive Andreev reflection signatures and surface state resonances at a superconductor interface.

Contribution

It reports the first observation of Fermi arc surface states via Andreev reflection and surface resonances in WTe$_2$, revealing their unique transport properties.

Findings

Detection of non-periodic subgap resistance resonances

Identification of Tomasch-like oscillations in topological surface states

Evidence of specific carrier transmission directions

Abstract

We experimentally investigate charge transport through the interface between a niobium superconductor and a three-dimensional WTe$_2$ Weyl semimetal. In addition to classical Andreev reflection, we observe sharp non-periodic subgap resistance resonances. From an analysis of their positions, magnetic field and temperature dependencies, we can interpret them as an analog of Tomasch oscillations for transport along the topological surface state across the region of proximity-induced superconductivity at the Nb-WTe$_2$ interface. Observation of distinct geometrical resonances implies a specific transmission direction for carriers, which is a hallmark of the Fermi arc surface states.