Identification of the Mott insulating CDW state in 1T-TaS$_2$

TL;DR

This study uses advanced DFT+U calculations to clarify the Mott insulating charge-density-wave state in 1T-TaS$_2$, resolving previous controversies about its electronic structure and emphasizing the importance of basis choice.

Contribution

It demonstrates that a generalized basis covering the David star is essential to accurately model electron correlation and reproduce the Mott insulating state in 1T-TaS$_2$.

Findings

Reproduces the Mott insulating state with layer-by-layer antiferromagnetic order.

Highlights the inadequacy of atomic-orbital basis in describing electron correlation.

Provides a methodology applicable to molecular solids with similar correlation issues.

Abstract

We investigate the low-temperature charge-density-wave (CDW) state of bulk TaS$_2$ with a fully self-consistent DFT+U approach, over which the controversy has remained unresolved regarding the out-of-plane metallic band. By examining the innate structure of the Hubbard U potential, we reveal that the conventional use of atomic-orbital basis could seriously misevaluate the electron correlation in the CDW state. By adopting a generalized basis, covering the whole David star, we successfully reproduce the Mott insulating nature with the layer-by-layer antiferromagnetic order. Similar consideration should be applied for description of the electron correlation in molecular solid.