Dynamical control of Coulomb interactions and Hubbard bands in monolayer 1T-TaS$_2$

TL;DR

This paper demonstrates how lattice distortions in monolayer 1T-TaS$_2$ modulate Coulomb interactions and Hubbard bands, enabling control over its Mott-insulating state via light-induced effects.

Contribution

It reveals the microscopic mechanism linking CDW amplitude, Coulomb interactions, and electronic phase transitions in 2D transition-metal dichalcogenides.

Findings

CDW amplitude alters bare and screened Coulomb interactions.

Hubbard bands shift with CDW amplitude.

Reduced distortion induces a Mott insulator to metal transition.

Abstract

Monolayer 1T-TaS$_2$ hosts a star-of-David charge-density wave (CDW) that stabilizes a low-temperature Mott-insulating state. Recent time-resolved spectroscopies indicate a coupling between the CDW amplitude mode and the electronic correlation strength, yet the role of the screened Coulomb interaction remains unclear. Using the constrained random-phase approximation, we show that the CDW amplitude modifies the bare and screened on-site interactions, leading to sizable variations in the effective Hubbard U. Our combined density functional and dynamical mean-field theory calculations reveal that the Hubbard bands shift in concert with the CDW amplitude, and that a reduced distortion drives a transition from a Mott insulator to a correlated metal. These results demonstrate a direct link between lattice distortions and Coulomb interactions in transition-metal dichalcogenides, providing a microscopic mechanism for light-induced control of correlated phases in two-dimensional quantum materials.