Unconventional orbital-charge density wave mechanism in transition metal dichalcogenide 1T-TaS2

TL;DR

This paper proposes a novel orbital-charge density wave mechanism in 1T-TaS2, explaining its incommensurate density wave state through a first-principles Hubbard model and paramagnon interference, revealing unique orbital and sign-reversal features.

Contribution

It introduces an unconventional orbital-charge density wave mechanism based on a Hubbard model and paramagnon interference, offering new insights into 1T-TaS2's density wave phenomena.

Findings

Identifies the orbital-selective nature of the density wave

Reveals unconventional sign-reversal in momentum and energy spaces

Provides a natural explanation for the incommensurate density wave in 1T-TaS2

Abstract

The transition metal dichalcogenide 1T-TaS2 attract growing attention because of the formation of rich density-wave (DW) and superconducting transitions. However, the origin of the incommensurate DW state at the highest temperature (~ 550 K), which is "the parent state" of the rich physical phenomena, is still uncovered. Here, we present a natural explanation for the triple-q incommensurate DW in 1T-TaS2 based on the first-principles Hubbard model with on-site U. We apply the paramagnon interference mechanism that gives the nematic order in Fe-based superconductors. The derived order parameter has very unique characters: (i) the orbital-selective nature, and (ii) the unconventional sign-reversal in both momentum and energy spaces. The present study will be useful for understanding rich physics in 1T-TaS2, 1T-VSe2, and other transition metal dichalcogenides.