Metal-insulator transition in organic ion intercalated VSe2 induced by dimensional crossover

The charge-density wave (CDW) transition has been extensively studied in transition metal dichalcogenides (TMDs), the underlying mechanism and the related metal-insulator transition are not as simple as Peierls instability in one dimension and still under hot debate. Here, through electrochemical intercalation of organic ions, we have observed a dimensional crossover induced metal-insulator transition in an organic ion intercalated TMDs: (TBA)(0.3) VSe2. In pristine VSe2, previous studies have revealed a three-dimensional CDW transition at T-CDW similar to 110 K with a metallic ground state. After intercalation of organic ions, the remarkable anisotropy of resistivity indicates a highly two-dimensional electronic state in (TBA)(0.3 )VSe2, which is consistent with our density functional theory (DFT) calculation. Interestingly, the dimensional crossover enhances the CDW transition with T-CDW of 165 K and leads to an insulating ground state in (TBA)(0.3) VSe2. Moreover, a commensurate superstructure with 3a x 3a periodicity is also confirmed in this insulating CDW state. Although the DFT calculation suggests that the commensurate superstructure and the enhanced CDW temperature could be ascribed to the improved Fermi surface nesting, whether the metal-insulator transition is driven by a perfect Fermi surface nesting is still elusive at the present stage. The possible role of electronic correlation and electron-phonon coupling has also been discussed. Our work provides a different material platform to study the metal-insulator transition in TMDs.