The coexistence and competition of charge-density wave and superconductivity in the electron-doped H- MX2 (M = Mo, W and X=S, Se)

Abstract

In the group VI transition metal dichalcogenides (TMDs), an insulator family with two-dimensional structure, MoS2 has recently demonstrated to be involved in charge-density wave (CDW) and superconductivity (SC). Nevertheless, there is a lack of a cohesive theoretical framework and fragmentation in the existing theoretical models of the relationship between CDW and SC for this system. Base on first-principles calculations, the effects of electron doping on the electronic properties, electron-phonon interaction and SC are investigated comprehensively for monolayer H- MX2 (M = Mo, W and X = S, Se) here. We confirmed that two CDW phases, 23×23 and 2 × 2, are originated from Fermi surface nesting (FSN) and electron-phonon coupling (EPC), respectively. A complicated phase diagram of doping concentration dependencies of CDW and SC critical temperatures (TC) is created, by SC coexisting with 23×23 CDW phase while competing with 2 × 2 CDW phase. The physical mechanisms of such coexistence and competition are also explained here. Our results extend the theoretical investigation by providing a comprehensive and in-depth analysis of CDW and SC in the group VI TMDs, and open up an alternative path for the exploration and regulation of collective phases of two-dimensional materials.