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Insulator-to-metal Mott transition facilitated by lattice deformation in monolayer $α$-RuCl$_3$ on graphite

Creating heterostructures with graphene/graphite is a practical method for charge-doping $α$-RuCl$_3$, but not sufficient to cause the insulator-to-metal transition. In this study, detailed scanning tunneling microscopy/spectroscopy measurements on $α$-RuCl$_3$ with various lattice deformations reveal that both in-plane and out-of-plane lattice distortions may collapse the Mott-gap in the case of monolayer $α$-RuCl$_3$ in proximity to graphite, but have little impact on its bulk form alone. In the Mott-Hubbard framework, the transition is attributed to the lattice distortion-facilitated substantial modulation of the electron correlation parameter. Observation of the orbital textures on a highly compressed monolayer $α$-RuCl$_3$ flake on graphite provides valuable evidence that electrons are efficiently transferred from the heterointerface into Cl3$p$ orbitals under the lattice distortion. It is believed that the splitting of Ru $t_{2g}$ bands within the trigonal distortion of Ru-Cl-Ru octahedra bonds generated the electrons transfer pathways. The increase of the Cl3$p$ states enhance the hopping integral in the Mott-Hubbard bands, resulting in the Mott-transition. These findings suggest a new route for implementing the insulator-to-metal transition upon doping in $α$-RuCl$_3$ by deforming the lattice in addition to the formation of heterostructure.