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arXiv · 2602.03937

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

Xian P. Yang·Chia-Hsiu Hsu·Gokul Acharya·Junyi Zhang·Md Shafayat Hossain·Tyler A. Cochran·Bimal Neupane·Zi-Jia Cheng·Santosh Karki Chhetri·Byunghoon Kim·Shiyuan Gao·Yu-Xiao Jiang·Maksim Litskevich·Jian Wang·Yuanxi Wang·Jin Hu·M. Zahid Hasan
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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.

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Xian P. Yang, Chia-Hsiu Hsu, Gokul Acharya, Junyi Zhang, Md Shafayat Hossain, Tyler A. Cochran, Bimal Neupane, Zi-Jia Cheng, Santosh Karki Chhetri, Byunghoon Kim, Shiyuan Gao, Yu-Xiao Jiang, Maksim Litskevich, Jian Wang, Yuanxi Wang, Jin Hu, M. Zahid Hasan. 2026-02-03. Observation of a structurally driven, reversible topological phase transition in a distorted square net material. https://arxiv.org/abs/2602.03937

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