Atomic structures and electronic correlation of monolayer 1T-TaSe2

TL;DR

This study uses density functional theory to explore the atomic and electronic structures of monolayer 1T-TaSe2, proposing an alternative structural model that explains experimental spectroscopic features without requiring strong electron correlation.

Contribution

It introduces an anion-centered cluster structural model for monolayer 1T-TaSe2, challenging the traditional cation-centered model and explaining spectroscopic data through band insulating behavior.

Findings

Anion-centered cluster structure reproduces experimental spectroscopic features.

The observed features are consistent with a band insulator, not a Mott insulator.

Structural flexibility plays a key role in the electronic properties.

Abstract

We investigate atomic and electronic structures of monolayer 1T-TaSe2 using density functional theory calculations. Monolayers of 1T-TaSe2 were recently grown on graphene substrates and suggested as an intriguing Mott insulator [Nat. Phys. 16, 218 (2020)]. However, the prevailing structural model for the model system of 1T-TaS2, the cation-centered cluster of a David-star shape with strong electron correlation, could not explain the characteristic and unusual orbital splitting observed in scanning tunneling spectroscopy experiments. We suggest an alternative structure model, an anion-centered cluster structure, which can reproduce most of the unusual spectroscopic characteristics with electron doping from the substrate without electron correlation. The unusual spectroscopic features observed, thus, seems to indicate a simple and usual band insulating state. This work indicates the importance of a large structural degree of freedom given for a cluster Mott insulator.