Interplay of Excitonic Charge Density Wave and Superconductivity in Transition Metal Dichalcogenides

Abstract

Motivated by the unique characteristics of the phase diagram of 1T-TiSe2, we investigated the complex interplay of excitonic charge density wave (CDW) and superconductivity (SC) on a two-dimensional triangular lattice, each site accommodating two orbitals. In response to various tuning parameters, such as intercalation, pressure, substitution, and gating, these materials exhibit a generic and gradual waning of CDW, followed by the emergence of SC. Intriguingly, the nature of CDW changes from commensurate to incommensurate with the appearance of SC. Setting up a minimal model based on observed excitonic CDW and electron and hole pockets in the Fermi surface, and analyzing it within a simple mean-field framework, we can comprehend some salient experimental features. We also found that the qualitative phase diagram remains insensitive to details of the band structure. These results offer crucial insights into the nature of the interplay between CDW and SC in transition-metal dichalcogenides.