Emergent Quantum Phenomena of Noncentrosymmetric Charge-Density Wave in 1T-Transition Metal Dichalcogenides

TL;DR

This paper reveals that a new anion-centered David star charge order in 1T-transition metal dichalcogenides breaks inversion symmetry, leading to flat bands with Rashba spin-orbit coupling and enabling novel quantum phenomena like spin Hall effects and Chern bands.

Contribution

It introduces and characterizes a new noncentrosymmetric charge structure in 1T-TMDs, showing its impact on electronic properties and potential quantum phenomena.

Findings

Breaks inversion symmetry in 1T-TMDs

Creates flat bands with Rashba spin-orbit coupling

Enables phenomena like spin Hall effect and Chern bands

Abstract

1T-transition metal dichalcogenides (TMD) have been an exciting platform for exploring the intertwinement of charge density waves and strong correlation phenomena. While the David star structure has been conventionally considered as the underlying charge order in the literature, recent scanning tunneling probe experiments on several monolayer 1T-TMD materials have motivated a new, alternative structure, namely the anion-centered David star structure. In this Letter, we show that this novel anion-centered David star structure manifestly breaks inversion symmetry, resulting in flat bands with pronounced Rashba spin-orbit couplings. These distinctive features unlock novel possibilities and functionalities for 1T-TMDs, including the giant spin Hall effect, the emergence of Chern bands, and spin liquid that spontaneously breaks crystalline rotational symmetry. Our findings establish promising avenues for exploring emerging quantum phenomena of monolayer 1T-TMDs with this novel noncentrosymmetric structure.