Single-layer 1T-TaSe2 has recently been found to host a Mott insulating ground state entwined with a commensurate charge density wave (CDW). However, the interplay between the CDW order and the Mott state remains unclear and elusive. Using first-principles calculations, we show that the CDW order with David-Star lattice distortions induces the formation of two different types of Ta-d orbitals (one is localized and the other is extended), and the Mott insulating state is brought on by the electron correlation on the localized orbital that is separated from the extended orbitals in energy. Interestingly, when a compressive biaxial strain is applied on monolayer 1T-TaSe2, the Mott-insulating phase will first transform to a charge-transfer insulating phase and then to a normal metallic phase with increasing strain. The CDW is always persisting and even enhanced under the strain, indicating that the Mottness collapse is unexpectedly not at the expense of the suppression of the long-range CDW order. We further reveal that the realization of the metallization in the CDW phase is because the localized orbital immerses into the extended-orbital-spanned Fermi sea and its Hubbard splitting is quenched by orbital hybridization. Our findings may provide significant implications for fine control over correlated electronic states, possessing potential applications in ultrafast resistive switching.

Mottness collapse in monolayer 1T-TaSe2 with persisting charge density wave order

ACS Spring Meeting 2021

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