Experimental evidence of large-gap two-dimensional topological insulator on the surface of ZrTe5

TL;DR

This study provides experimental evidence that the surface of ZrTe5 hosts a large-gap two-dimensional topological insulator, confirmed by spectroscopy and calculations, promising for high-temperature spintronic applications.

Contribution

The paper experimentally verifies that the top monolayer of ZrTe5 is a large-gap 2D topological insulator, combining spectroscopy and first-principles calculations.

Findings

Large surface band gap of ~100 meV in ZrTe5 monolayer

Presence of finite density-of-states at step edges

Confirmation of topologically nontrivial edge states

Abstract

Two-dimensional (2D) topological insulators (TIs) with a large bulk band-gap are promising for experimental studies of the quantum spin Hall effect and for spintronic device applications. Despite considerable theoretical efforts in predicting large-gap 2D TI candidates, only few of them have been experimentally verified. Here, by combining scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy, we reveal that the top monolayer of ZrTe5 crystals hosts a large band gap of ~100 meV on the surface and a finite constant density-of-states within the gap at the step edge. Our first-principles calculations confirm the topologically nontrivial nature of the edge states. These results demonstrate that the top monolayer of ZrTe5 crystals is a large-gap 2D TI suitable for topotronic applications at high temperature.