Kavli Affiliate: Gang Su
| First 5 Authors: Xing-Zhou Qu, Xing-Zhou Qu, , ,
| Summary:
Understanding the pairing mechanism in bilayer nickelate superconductors
constitutes a fascinating quest. Here we investigate the intriguing interplay
between Hund’s rule coupling and interorbital hybridization in a two-orbital
model for bilayer nickelates, using a comprehensive tensor network approach:
density matrix renormalization group for finite-size systems, infinite
projected entangled-pair states in the thermodynamic limit, and thermal tensor
networks for finite-temperature properties. We explain the pressure-dependent
high-$T_c$ superconductivity observed in experiment, by identifying 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 $K_mathrmSC$. However, the former
exhibits a much stronger amplitude than the latter, with a distinctly higher SC
characteristic temperature $T_c^*$, below which the pairing susceptibility
diverges as $chi_mathrmSC(T) sim 1/T^2-K_mathrmSC$. 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
with 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. Our results offer a comprehensive
understanding of the interlayer pairing in superconducting La$_3$Ni$_2$O$_7$.
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