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

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.