Mottness in two-dimensional van der Waals Nb${}_3$X${}_8$ monolayers (X=Cl, Br, and I)

Abstract

We investigate strong electron-electron correlation effects on 2-dimensional van der Waals materials Nb${}_3$X${}_8$ (X=Cl, Br, I). We find that the monolayers Nb${}_3$X${}_8$ 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 $\approx$ 5 $\sim$ 10. Both Mott and magnetic transitions of the material are calculated by the slave boson mean field theory. Doping the Mott state, a $d_{x^2-y^2}+i{d}_{xy}$ superconducting pairing instability is found. We also construct a tunable bilayer Hubbard system for two sliding Nb${}_3$X${}_8$ layers. The bilayer system displays a crossover between the band insulator and Mott insulator.

10 pages, 6 figures in the main text, and 4 pages, 2 figures in the supplemental material

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• Momentum-Resolved Fingerprint of Mottness in Layer-Dimerized Nb${}_3$Br${}_8$
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