LK-99, with chemical formula Pb$_{10-x}$Cu$_x$(PO4)$_6$O, was recently reported to be a room-temperature superconductor. While this claim has met with little support in a flurry of ensuing work, a variety of calculations (mostly based on density-functional theory) have demonstrated that the system possesses some unusual characteristics in the electronic structure, in particular flat bands. We have established previously that within DFT, the system is insulating with many characteristics resembling the classic cuprates, provided the structure is not constrained to the $P$3(143) symmetry nominally assigned to it. Here we describe the basic electronic structure of LK-99 within self-consistent many-body perturbative approach, quasiparticle self-consistent GW (QSGW) approximation and their diagrammatic extensions. QSGW predicts that pristine LK-99 is indeed a Mott/charge transfer insulator, with a bandgap gap in excess of 3eV, whether or not constrained to the $P$3(143) symmetry. The highest valence bands occur as a pair, and look similar to DFT bands. The lowest conduction band is an almost dispersionless state of largely Cu $d$ character. When Pb$_9$Cu(PO$_4$)$_6$O} is hole-doped, the valence bands modify only slightly, and a hole pocket appears. However, two solutions emerge: a high-moment solution with the Cu local moment aligned parallel to neighbors, and a low-moment solution with Cu aligned antiparallel to its environment. In the electron-doped case the conduction band structure changes significantly: states of mostly Pb character merge with the formerly dispersionless Cu $d$ state, and high-spin and low spin solutions once again appear. Thus we conclude that with suitable doping, the ground state of the system is not adequately described by a band picture, and that strong correlations are likely.

arxiv.org

방 전자 구조의 다중행렬식로 전이 : Pb10-xCux(PO4)6O는 최근에 상온에서 초전도를 보인다고 주장된 물질이다. 이 논문에서는 이 물질의 전자 구조를 QSGW와 QSGWˆ 방법으로 연구하였다. QSGW는 다체

gall.dcinside.com