Mottness in two-dimensional van der Waals Nb3X8 monolayers (X=Cl, Br, and I)

[摘要] We investigate strong electron-electron correlation effects on two-dimensional van der Waals materials Nb3X8 (X = Cl, Br, I). We find that the monolayers Nb3X8 are ideal systems close to the strong correlation limit. They can be described by a half-filled single band Hubbard model in which the ratio between the Hubbard, U, and the bandwidth, W, U/W approximate to 5-10. Both Mott and magnetic transitions of the material are calculated by the slave boson mean-field theory. Doping the Mott state, a dx2-y2 + idxy superconducting pairing instability is found. We also construct a tunable bilayer Hubbard system for two sliding Nb3X8 layers. The bilayer system displays a crossover between the band insulator and Mott insulator.

[关键词] MAGIC-ANGLE;INSULATOR;SUPERCONDUCTIVITY;APPROXIMATION;TRANSITION;SYSTEMS;PHYSICS;DIODE;STATE;SPIN