Exploring the 4d1analogue of cuprates: theoretical studies on bulk NbF4and NbF4monolayer stabilized on MgO (001) plane.

The recent research in infinite-layer nickelates has inspired new effort in finding the cuprate analogs. Here we propose that NbF4, which contains niobium-centered fluorine octahedra, is a promising 4d1analogue of cuprates. Using the density functional theory, we first show that bulk NbF4is in close proximity tod1configuration, with Nb4dxyorbital nearly half-filled. A single band with dominating4dxycharacter crosses the Fermi level, forming a square-like Fermi surface. The intralayer G-type antiferromagnetic (AFM) order is energetically favored and the Coulomb interaction drives the system into an AFM insulator. Next we demonstrate that the NbF4layer can be stabilized on MgO substrate with main electronic and magnetic features retained, offering an alternative route to realize the NbF4-related high-Tcsuperconductors. Furthermore, we derive effective single orbital models for both systems and investigate the electron correlation effects via functional renormalization group. We find that the G-type AFM dominates near half-filling butdx2-y2-wave superconductivity (SC) prevails upon suitable hole/electron doping. Based on the striking similarities between NbF4and cuprates, we suggest that NbF4-related compounds may be exotic candidates for searching new high-Tcsuperconductors.