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

doi:10.1103/spbv-1xg6

Structurally Driven, Reversible Topological Phase Transition in a Distorted Square Net Material

Xian P. Yang ^1,*, Chia-Hsiu Hsu^2,3, Gokul Acharya⁴, Junyi Zhang ⁵, Md Shafayat Hossain ¹, Tyler A. Cochran¹, Bimal Neupane ⁶, Zi-Jia Cheng¹, Santosh Karki Chhetri ⁴ et al.

Byunghoon Kim¹, Shiyuan Gao⁵, Yu-Xiao Jiang¹, Maksim Litskevich ¹, Jian Wang⁷, Yuanxi Wang⁶, Jin Hu^4,8, and M. Zahid Hasan^1,9,10,†

¹Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey, USA
²Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
³Quantum Materials Science Unit, Okinawa Institute of Science and Technology (OIST), Okinawa 904-0495, Japan
⁴Department of Physics, University of Arkansas, Fayetteville, Arkansas, USA
⁵Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland, USA
⁶Department of Physics, University of North Texas, Denton, Texas, USA
⁷Department of Chemistry and Biochemistry, Wichita State University, Wichita, Kansas, USA
⁸Materials Science and Engineering Program, Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas, USA
⁹Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, New Jersey, USA
¹⁰Lawrence Berkeley National Laboratory, Berkeley, California, USA

^*Contact author: xiany@princeton.edu
^†Contact author: mzhasan@princeton.edu

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Phys. Rev. Lett. 136, 116603 – Published 17 March, 2026

DOI: https://doi.org/10.1103/spbv-1xg6

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 subsurface 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 subsurface layer in GdPS offers a unique route for exploring and controlling topological states in bulk materials.

Physical Review Letters

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Structurally Driven, Reversible Topological Phase Transition in a Distorted Square Net Material

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