Pb10−x Cu x (PO4)6O: a Mott or charge transfer insulator in need of further doping for (super)conductivity

Abstract

Abstract We briefly review the status quo of research on the putative superconductor Pb9Cu(PO4)6O also known as LK-99. Further, we provide ab initio derived tight-binding parameters for a two- and five-band model, and solve these in dynamical-mean-field theory. The interaction-to-bandwidth ratio makes LK-99 a Mott or charge transfer insulator. Electron or hole doping (which is different from substituting Pb by Cu and thus differs from LK-99) is required to make it metallic and potentially superconducting.