Flat bands promoted by Hund's rule coupling in the candidate double-layer high-temperature superconductor La_3Ni_2O_7
arXiv (Cornell University)(2023)
摘要
We report strongly correlated electronic band structure calculations of the
recently discovered double-layer high-temperature superconductor
La_3Ni_2O_7 under pressure. Our calculations reveal dual nature of Ni-d
electrons with almost localized d_z^2 orbitals due to onsite Coulomb
repulsion and very flat hybridization bands of Ni-d_x^2-y^2 and
Ni-d_z^2 quasiparticles near the Fermi energy. We find that the
quasiparticle effective mass are greatly enhanced by the Hund's rule coupling
and their lifetimes are inversely proportional to the temperature, which
explains the experimentally observed strange metal behavior in the normal
state. We also find strong antiferromagnetic spin correlations of Ni-d
electrons, which may provide the pairing force of quasiparticles for the
high-temperature superconductivity. These give a potential explanation of two
key observations in experiment and connect the superconducting
La_3Ni_2O_7 with cuprate high-temperature superconductors. The presence
of flat bands and the interplay of orbital-selective Mott, Hund, and Kondo
physics make La_3Ni_2O_7 a unique platform for exploring rich emergent
quantum many-body phenomena in the future.
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关键词
flat bands,high-temperature high-temperature,double-layer
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