Kavli Affiliate: Gang Su
| First 5 Authors: Xing-Zhou Qu, Dai-Wei Qu, Xin-Wei Yi, Wei Li, Gang Su
| Summary:
Understanding the pairing mechanism in bilayer nickelate superconductors
constitutes a fascinating quest. Using density matrix renormalization group for
$T=0$ and thermal tensor networks for $T>0$ properties, along with density
functional theory calculations, we investigate the intriguing interplay between
the Hund’s rule coupling and interorbital hybridization that explains the
pressure-dependent high-$T_c$ superconductivity in bilayer nickelates. By
studying a two-orbital model, we identify three distinct superconductive (SC)
regimes: hybridization dominant, Hund’s rule dominant, and the hybrid-Hund
synergistic SC regimes. In these SC regimes, both $d_{x^2-y^2}$ and $d_{z^2}$
orbitals exhibit algebraic pairing correlations with similar Luttinger
parameters $K_{rm SC}$. In particular, the former always exhibits a much
stronger amplitude than the latter, with a distinctly higher SC characteristic
temperature $T_c^*$. Below this temperature, the pairing susceptibility
diverges as $chi_{rm SC}(T) sim 1/T^{2-K_{rm SC}}$. With realistic model
parameters, we find the pressurized La$_3$Ni$_2$O$_7$ falls into the Hund’s
rule dominated SC regime. As hybridization further enhances under pressure, it
leads to significant interorbital frustration and in turn suppresses the SC
correlations, explaining the rise and fall of high-$T_c$ superconductivity
under high pressure [J. Li, et al., arXiv:2404.11369 (2024)]. Our results offer
a comprehensive understanding of the interlayer pairing in superconducting
La$_3$Ni$_2$O$_7$.
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