Mott transition and superconductivity in the Dirac moiré band of a Γ-valley TMD system

Recent experiments have observed a Dirac-Mott transition in the twisted ABBA WSe₂ system [1]. The moiré physics in this system is dominated by the Γ-valley bands which possess negligible spin-orbit coupling. We construct an effective tight-binding description for the active Γ-valley moiré bands at hole doping ν = 2. By projecting the screened Coulomb interaction onto the Wannier orbitals, we derive an extended Hubbard model that captures the Γ- valley physics of the system. We calculate the quasiparticle weight at different twist angles using the slave spin method. We observe that the quasiparticle weight decreases as the twist angle is reduced, vanishing at a critical angle θ_c, which signals the Mott transition. On the verge of the Dirac-Mott transition, incoherent electron excitations mediate an electron-electron spin exchange interaction. We estimate the strength of the exchange interaction in this regime and find that it is maximized near the Mott transition. We discuss the possible superconducting pairing in this regime.

[1] L. Ma, et al, Nature Materials (2025).