Flat bands promoted by Hund's rule coupling in the candidate double-layer high-temperature superconductor La3Ni2O7 under high pressure
Yingying Cao, Yi-feng Yang
DOI 10.1103/PhysRevB.109.L081105 · Physical Review B
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Abstract
Experiments in the high-temperature superconductor La3Ni2O7 have revealed both high Tc and strange metal behaviors over a wide pressure range. While first-principles density functional theory has predicted weakly correlated bands that cannot explain these key observations, we report here strongly correlated electronic band structure calculations that reveal the dual nature of Ni-d electrons with almost localized dz2 orbitals due to on-site Coulomb repulsion and flat bands of Ni-dx2−y2 and Ni-dz2 quasiparticles near the Fermi energy. We find that the quasiparticle effective masses are greatly enhanced by Hund's rule coupling and their lifetimes are inversely proportional to temperature, which explains the experimentally observed strange metal behavior in the normal state. Our calculations also reveal strong antiferromagnetic spin correlations of Ni-d electrons, which may provide the pairing force of quasiparticles for high-temperature superconductivity. The presence of flat bands and the interplay of orbital-selective Mott, Hund, and Kondo physics lay the basis for a two-component theory of its pairing mechanism and make La3Ni2O7 a unique platform for exploring rich emergent quantum many-body phenomena in the future.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| La3Ni2O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 80 | 29.5 GPa | unknown |
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