Observation of a structurally driven, reversible topological phase transition in a distorted square net material

TL;DR

This study demonstrates a reversible topological phase transition in GdPS triggered by potassium dosing, showing a cascade of topological states driven by structural distortions, with potential for controlling topological phases in bulk materials.

Contribution

We reveal a structurally driven, reversible topological phase transition in GdPS induced by potassium adsorption, advancing control over topological states in layered materials.

Findings

Transition from trivial band gap to Dirac cone state

Observation of a 2 eV dispersion in the Dirac cone

Transition to a two-dimensional topological insulator

Abstract

Topological materials hold immense promise for exhibiting exotic quantum phenomena, yet achieving controllable topological phase transitions remains challenging. Here, we demonstrate a structurally driven, reversible topological phase transition in the distorted square net material GdPS, induced via in situ potassium dosing. Using angle-resolved photoemission spectroscopy and first principles calculations, we demonstrate a cascade of topological phases in the sub-surface P layer: from a large, topologically trivial band gap to a gapless Dirac cone state with a 2 eV dispersion, and finally to a two-dimensional topological insulator as inferred from theory. This evolution is driven by subtle structural distortions in the first P layer caused by potassium adsorption, which in turn contribute to the band gap closure and topological phase transition. Furthermore, the ability to manipulate the topology of a sub-surface layer in GdPS offers a unique route for exploring and controlling topological states in bulk materials.