Pb_10−x Cu_x(PO₄)₆O: a Mott or charge transfer insulator in need of further doping for (super)conductivity

Abstract

We briefly review the status quo of research on the putative superconductor Pb₉Cu(PO₄)₆O also known as LK-99. Further, we provide<i>ab initio</i>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.