Electronic structure of the putative room-temperature superconductor Pb${}_9$Cu(PO${}_4$)${}_6$O

Abstract

A recent paper [Lee {\em et al.}, J. Korean Cryt. Growth Cryst. Techn. {\bf 33}, 61 (2023)] provides some experimental indications that Pb${}_{10-x}$Cu${}_x$(PO${}_4$)${}_6$O with $x\approx 1$, coined LK-99, might be a room-temperature superconductor at ambient pressure. Our density-functional theory calculations show lattice parameters and a volume contraction with $x$ -- very similar to experiment. The DFT electronic structure shows Cu${}^{2+}$ in a $3d^9$ configuration with two flat Cu bands crossing the Fermi energy. This puts Pb${}_9$Cu(PO${}_4$)${}_6$O in an ultra-correlated 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 an correlation-enhanced electron-phonon mechanism, whereas a diamagnet without superconductivity appears to be rather at odds with our results.

10 pages, 7 figures and 4 tables including supplementary materials

References in corpus (6)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Superconducting Transitions in Flat Band Systems
• First-principles study on the electronic structure of Pb${}_{10-x}$Cu${}_x$(PO${}_4$)${}_6$O ($x$=0, 1)
• Revealing the Coulomb interaction strength in a cuprate superconductor
• Ferromagnetic and insulating behavior in both half magnetic levitation and non-levitation LK-99 like samples

Cited by in corpus (3)

• Single crystal synthesis, structure, and magnetism of Pb${}_{10-x}$Cu${}_x$(PO${}_4$)${}_6$O
• Symmetry breaking induced insulating electronic state in Pb${}_9$Cu(PO${}_4$)${}_6$O
• No superconductivity in Pb${}_9$Cu${}_1$(PO${}_4$)${}_6$O found in orbital and spin fluctuation exchange calculations