Exploring the 4d1 analogue of cuprates: theoretical studies on bulk NbF4 and NbF4 monolayer stabilized on MgO (001) plane

Abstract The recent research in infinite-layer nickelates has inspired new effort in finding the cuprate analogs. Here we propose that NbF 4 , which contains niobium-centered fluorine octahedra, is a promising 4 d 1 analogue of cuprates. Using the density functional theory, we first show that bulk NbF 4 is in close proximity to d 1 configuration, with Nb 4 d x y orbital nearly half-filled. A single band with dominating 4 d x y character 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 NbF 4 layer can be stabilized on MgO substrate with main electronic and magnetic features retained, offering an alternative route to realize the NbF 4 -related high- T c superconductors. 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 but d x 2 − y 2 -wave superconductivity (SC) prevails upon suitable hole/electron doping. Based on the striking similarities between NbF 4 and cuprates, we suggest that NbF 4 -related compounds may be exotic candidates for searching new high- T c superconductors.