Pairing Symmetry Crossover from $d$-wave to $s_{\pm }$-wave in a Bilayer Nickelate Driven by Hund's Coupling and Crystal Field Splitting

Abstract

The pairing symmetry of the recently discovered bilayer nickelate superconductor La${}_3$Ni${}_2$O${}_7$ is a subject of intense debate in condensed matter physics, with the two leading theoretical candidates being a sign-reversing $s_{\pm }$-wave and a $d$-wave state. To investigate its ground-state properties in the intermediate coupling regime which is critical for real materials, we construct a two-orbital bilayer Hubbard model and employ the constrained-path quantum Monte Carlo method for large-scale simulations. By systematically calculating ground-state pairing correlation functions across parameter spaces, we map its pairing symmetry phase diagram. We find that an increasing Hund's coupling selectively enhances the interlayer $s_{\pm }$-wave pairing while suppressing the intralayer $d$-wave pairing. Similarly, a larger crystal field splitting drives a transition from $d$-wave- to $s_{\pm }$-wave-dominant states. Further analysis reveals that the strength of the intralayer $d$-wave pairing is strongly correlated with the $(\pi ,\pi )$ antiferromagnetic spin fluctuations, which are in turn effectively suppressed by a large crystal field splitting, thereby weakening the $d$-wave pairing channel. Additionally, the dominant pairing symmetry transition region roughly overlaps with the inversion of orbital occupancy response to Hubbard $U$, suggesting an intrinsic link between pairing competition and orbital physics. Our results indicate that, within the parameter regime relevant to the actual material, the $s_{\pm }$-wave is the most probable pairing symmetry.

9 pages, 6 figures

References in corpus (4)

• Computational complexity and fundamental limitations to fermionic quantum Monte Carlo simulations
• Quantum Monte Carlo Study of Pairing Symmetry and Correlation in Iron-based Superconductors
• Theory of magnetic excitations in multilayer nickelate superconductor La${}_3$Ni${}_2$O${}_7$
• Electronic structures and superconductivity in Nd-doped La${}_3$Ni${}_2$O${}_7$

Cited by in corpus (2)

• Compressive Strain Turns $s^{\pm }$ into $d$-Wave Pairing in One-unit-cell La${}_3$Ni${}_2$O${}_7$ Thin Film Via Substrate-Induced Hole Doping
• Tuning superconducting pairing symmetry via a staggered potential in the doped honeycomb Hubbard model