An LDA+DMFT study*

Transition metal dichalcogenides (TMDCs) often occur in two different crystal phases with octahedral (1T) and trigonal prismatic (2H) symmetry. For NbSe₂, the 2H phase has been known to be the most stable and easier to synthesize polymorph. However, recently 1T-NbSe₂ in the monolayer limit was synthesized epitaxially on a bilayer graphene and was suggested to be a Mott insulator [Yuki Nakata et al. NPG Asia Materials (2016) 8, e321] with √13 × √13 periodic density modulation. We perform ab-initio calculations to understand the emergence of an insulating behavior and charge density wave (CDW) in the monolayer 1T-NbSe₂, which otherwise is predicted to be a metal in DFT and GW calculations. We provide an estimate for the local and non-local screened Coulomb interaction within the ab-initio formalism and present the findings of LDA+DMFT simulations that suggest the possibility of opening of a Mott insulating gap in the CDW phase.