Physical Chemistry Chemical Physics, (2026)

Direct measurement of the temperature dependent lattice and electronic structure reconfigurations of α-RuCl₃ thin films

Peixuan Ji¹, Jin Chen¹, Jiapeng Wang¹, Liangpeng Hou¹, Huihui Liang¹, Jiaying Duan¹, Xiaochen Hong^2,3, Xi Chen⁴, Zhixin Hu⁴, Bernd Büchner², Xiaosong Wu⁵, Yanqing Ma^1,6, Zhixiang Sun⁴ and Lei Ma^1,6

1 Tianjin International Center for Nanoparticles and Nanosystems, Tianjin University, Tianjin 300072, P.R. China.

2 IFW-Dresden, 01069 Dresden, Germany.

3 Fakultät für Mathematik und Naturwissenschaften, Bergische Universität Wuppertal, 42097 Wuppertal, Germany.

4 Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, Tianjin 300072, P.R. China.

5 School of Physics, Peking University, Beijing 100871, P.R. China; 6. Tianjin Key Laboratory for Low-dimensional Electronic Materials and Advanced Instrumentation, Tianjin 300072, P.R. China.

6 Tianjin Key Laboratory for Low-dimensional Electronic Materials and Advanced Instrumentation, Tianjin 300072, P.R. China.

* zsun@tju.edu.cn, lei.ma@tju.edu.cn

Abstract

Herein, we reveal the temperature-dependent broadening of the Mott gap in layered α-RuCl₃, together with a distinct transition in the range of 100-130 K, through surface morphology and electronic structure characterizations using scanning tunneling microscopy and scanning tunneling spectroscopy, respectively. Furthermore, layer-dependent measurements indicate an enhanced phase transition and Kitaev interactions with decreasing thickness. These results show that low-dimensional α-RuCl₃ films differ from their bulk state owing to their unique structural and electronic properties, providing an ideal model platform for exploring Kitaev physics.