Multiple Slater Determinants and Strong Spin-Fluctuations as Key Ingredients of the Electronic Structure of Electron- and Hole-Doped Pb<sub>10−<i>x</i></sub>Cu<sub><i>x</i></sub>(PO<sub>4</sub>)<sub>6</sub>O
LK-99, with chemical formula Pb<sub>10−<i>x</i></sub>Cu<sub><i>x</i></sub>(PO<sub>4</sub>)<sub>6</sub>O, was recently reported to be a room-temperature superconductor. While this claim has met with little support in a flurry of...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Crystals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4352/15/7/621 |
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| Summary: | LK-99, with chemical formula Pb<sub>10−<i>x</i></sub>Cu<sub><i>x</i></sub>(PO<sub>4</sub>)<sub>6</sub>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 <i>P</i>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 <i>GW</i> (QS<i>GW</i>) approximation and their diagrammatic extensions. QS<i>GW</i> predicts that pristine LK-99 is indeed a Mott/charge transfer insulator, with a bandgap gap in excess of 3 eV, whether or not constrained to the <i>P</i>3(143) symmetry. When Pb<sub>9</sub>Cu(PO<sub>4</sub>)<sub>6</sub>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 <i>d</i> 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. Irrespective of whether this system class hosts superconductivity or not, the transition of Pb<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>O from being a band insulator to Pb<sub>9</sub>Cu(PO<sub>4</sub>)<sub>6</sub>O, a Mott insulator, and multi-determinantal nature of doped Mott physics make this an extremely interesting case-study for strongly correlated many-body physics. |
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| ISSN: | 2073-4352 |