Giant renormalization of correlation strength in 1T-TaS2 by lattice vibration

TL;DR

This study demonstrates that lattice vibrations significantly renormalize the electronic correlation strength in 1T-TaS2, causing a giant reduction in the band gap with temperature, linked to charge density wave effects.

Contribution

It reveals a large temperature-dependent renormalization of electronic correlations in 1T-TaS2 driven by lattice vibrations, using ab initio molecular dynamics and DFT+U calculations.

Findings

Band gap shrinks by half from 0 K to 200 K

Giant temperature dependence exceeds typical thermal effects

Linked to charge density wave and Mottness in 1T-TaS2

Abstract

The lattice thermodynamics of a 1T-TaS2 layer, e.g. the spontaneous formation of a sqrt13*sqrt13 commensurate charge density wave (CCDW) and vibrations around the equilibrium position, is calculated by ab initio molecular dynamics. Based on that, we examine how the ground-state electronic structure is renormalized by lattice temperature. We show that the band gap within the density functional theory plus onsite-U correction shrinks by half when the temperature raises from 0 K to 200 K. The gap size reduction is one order of magnitude larger than the temperature variation in energy. This giant temperature dependence is closely related to the CCDW-triggered Mottness in 1T-TaS2, and is expected to result in unconventional thermodynamic properties.