One-Dimensional Edge Transport in Few-Layer WTe$_2$

TL;DR

This study demonstrates the existence of topologically protected one-dimensional edge states in few-layer WTe$_2$, a candidate higher-order topological insulator, through Josephson effect measurements revealing their unique transport properties.

Contribution

It provides experimental evidence of 1D edge states in WTe$_2$ and identifies its topological nature as a higher-order topological insulator using Josephson transport techniques.

Findings

Observation of 1D edge states via Josephson effect

Robust Josephson transport over micrometer distances

Nonsinusoidal current-phase relation indicating topological states

Abstract

WTe$_2$ is a layered transitional-metal dichalcogenide (TMD) with a number of intriguing topological properties. Recently, WTe$_2$ has been predicted to be a higher-order topological insulator (HOTI) with topologically protected hinge states along the edges. The gapless nature of WTe$_2$ complicates the observation of one-dimensional (1D) topological states in transport due to their small contribution relative to the bulk. Here, we study the behavior of the Josephson effect in magnetic field to distinguish edge from bulk transport. The Josephson effect in few-layer WTe$_2$ reveals 1D states residing on the edges and steps. Moreover, our data demonstrates a combination of Josephson transport properties observed solely in another HOTI - bismuth, including Josephson transport over micrometer distances, extreme robustness in a magnetic field, and nonsinusoidal current-phase relation (CPR). Our observations strongly suggest the topological origin of the 1D states and that few-layer WTe$_2$ is a HOTI.