Ni-based transition metal trichalcogenide monolayer: A strongly correlated quadruple-layer graphene

Abstract

We investigate the electronic physics of layered Ni-based trichalcogenide ${\mathrm{NiPX}}_{3}$ (X = S, Se), a member of transition metal trichalcogenides (TMTs) with the chemical formula ${\mathrm{ABX}}_{3}$. These Ni-based TMTs distinguish themselves from other TMTs as their low energy electronic physics can be effectively described by the two ${e}_{g} d$ orbitals. The major band kinematics is characterized by the unusual long-range effective hopping between two third nearest-neighbor (TNN) Ni sites in the two-dimensional Ni honeycomb lattice so that the Ni lattice can be equivalently viewed as four weakly coupled honeycomb sublattices. Within each sublattice, the electronic physics is described by a strongly correlated two-orbital graphene-type model that results in an antiferromagnetic (AFM) ground state near half-filling. We show that the low energy physics in a paramagnetic state is determined by the eight Dirac cones which locate at $K, {K}^{\ensuremath{'}}, \frac{K}{2}$, and $\frac{{K}^{\ensuremath{'}}}{2}$ points in the first Brillouin zone with a strong AFM fluctuation between two $K ({K}^{\ensuremath{'}})$ and $\frac{{K}^{\ensuremath{'}}}{2} (\frac{K}{2})$ Dirac cones and carrier doping can sufficiently suppress the long-range AFM order and allow other competing orders, such as superconductivity, to emerge. The material can be an ideal system to study many exotic phenomena emerged from strong electron-electron correlation, including a potential $d\ifmmode\pm\else\textpm\fi{}id$ superconducting state at high temperature.