Nanoscale Determination of the Metal-Insulator Transition in Intercalated Bulk VSe<sub>2</sub>.

Ma, Wanru; Yang, Ye; Liang, Zuowei; Wu, Ping; Meng, Fanbao; Wang, Zhenyu; Chen, Xianhui · Nano Lett · 2025

basic_science · Level V

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Abstract

Two-dimensional (2D) materials provide unique opportunities to realize emergent phenomena by reducing their dimensionality. Using scanning tunneling microscopy combined with first-principles calculations, we determine an intriguing case of a metal-insulator transition (MIT) in a bulk compound, (TBA)<sub>0.3</sub>VSe<sub>2</sub>. Atomic-scale imaging reveals that the initial 4a<sub>0</sub> × 4a<sub>0</sub> charge density wave (CDW) order in 1T-VSe<sub>2</sub> transforms to √7a<sub>0</sub> × √3a<sub>0</sub> ordering upon intercalation, which is associated with an insulating gap with a magnitude of up to approximately 115 meV. Our calculations reveal that this energy gap is highly tunable through electron doping introduced by the intercalant. Moreover, the robustness of the √7a<sub>0</sub> × √3a<sub>0</sub> CDW order against the Lifshitz transition points to the key role of electron-phonon interactions in stabilizing the CDW state. Our work clarifies a rare example of a CDW-driven MIT in quasi-2D materials and establishes cation intercalation as an effective pathway for tuning both the dimensionality and the carrier concentration without inducing strain or disorder.