Observation of quantum spin Hall states in Ta$_2$Pd$_3$Te$_5$

TL;DR

This paper provides experimental evidence that Ta$_2$Pd$_3$Te$_5$ is a two-dimensional topological insulator exhibiting quantum spin Hall states, confirmed through multiple measurement techniques and theoretical calculations.

Contribution

It reports the discovery of a new 2D topological insulator, Ta$_2$Pd$_3$Te$_5$, with experimental validation of its topological properties.

Findings

Ta$_2$Pd$_3$Te$_5$ is a 2D topological insulator.

Presence of a band gap and topological edge states confirmed.

Potential for spintronic device applications.

Abstract

Two-dimensional topological insulators (2DTIs), which host the quantum spin Hall (QSH) effect, are one of the key materials in next-generation spintronic devices. To date, experimental evidence of the QSH effect has only been observed in a few materials, and thus, the search for new 2DTIs is at the forefront of physical and materials science. Here, we report experimental evidence of a 2DTI in the van der Waals material Ta$_2$Pd$_3$Te$_5$. First-principles calculations show that each monolayer of Ta$_2$Pd$_3$Te$_5$ is a 2DTI with weak interlayer interactions. Combined transport, angle-resolved photoemission spectroscopy, and scanning tunneling microscopy measurements confirm the existence of a band gap at the Fermi level and topological edge states inside the gap. These results demonstrate that Ta$_2$Pd$_3$Te$_5$ is a promising material for fabricating spintronic devices based on the QSH effect.