Electronic structure of the putative room-temperature superconductor Pb9Cu(PO4)6O

Abstract

A recent paper [ Lee , J. Kor. Cryst. Growth Cryst. Technol. 33, 61 (2023)10.6111/JKCGCT.2023.33.2.061 ] provides some experimental indications that Formula Presented with Formula Presented, coined LK-99, might be a room-temperature superconductor at ambient pressure. Our density-functional theory (DFT) calculations show lattice parameters and a volume contraction with Formula Presented, very similar to experiment. The DFT electronic structure shows Formula Presented in a Formula Presented configuration with two flat Cu bands crossing the Fermi energy. This puts Formula Presented in an ultracorrelated regime and suggests that, without doping, it is a Mott or charge-transfer insulator. If doped, such an electronic structure might support flat-band superconductivity or a correlation-enhanced electron-phonon mechanism, whereas a diamagnet without superconductivity appears to be rather at odds with our results.