Source capture
Authors Guijing Duan, Yunlong Wang, Zhiguang Liao, Changle Liu, Rong Yu
arXiv / Publisher http://arxiv.org/abs/2601.06440v1
PDF https://arxiv.org/pdf/2601.06440v1
Relevance score 4.372
Primary category Not available in this batch.
Published Not available in this batch.
Research paradigm Theoretical
Sample form Unknown

Summary

This study investigates a quarter-hole-filled two-orbital bilayer Hubbard model inspired by transition metal bilayer systems. By explicitly treating the strong interlayer bonding of the dz2 orbital in a molecular orbital basis and projecting out high-energy electronic states, we derive a low-energy effective Kugel-Khomskii Hamiltonian that describes the coupling between electron spins and layer pseudospins. Combining Weiss mean-field theory with generalized flavor-wave theory, we reveal a rich ground-state phase diagram, including ferromagnetic and antiferromagnetic phases accompanied by layer-staggered charge-density order, a layer-coherent phase with spontaneous interlayer quantum coherence, and a novel maximal spin-layer entangled phase. This entangled phase arises from an emergent O(4) symmetry that is spontaneously broken to O(3), and its excitation spectrum features three gapless Goldstone modes that are entangled. The results suggest a geometry-driven mechanism for realizing composite entanglement in strongly correlated bilayer systems, and provide a concrete theoretical framework for understanding bilayer nickelate superconductors and other multi-component correlated materials.

Materials

Methods

  • Weiss mean-field theory
  • Generalized flavor-wave theory
  • Schrieffer-Wolff transformation

Keywords

  • kugel khomskii hamiltonian
  • spin layer entangled phase
  • emergent o(4) symmetry
  • maximal spin layer entanglement
  • goldstone modes

Highlights

  • Our results uncover a geometrically driven mechanism for realizing composite entanglement in strongly correlated bilayer systems.
  • Provides a concrete theoretical framework relevant to bilayer nickelate superconductors and other multi-component correlated materials.

Conclusions

  • A rich ground-state phase diagram is revealed including ferromagnetic and antiferromagnetic phases with layer-staggered charge-density order, a layer-coherent phase with spontaneous interlayer quantum coherence, and a novel spin-layer-entangled (SLE) phase.
  • The SLE phase arises from the spontaneous breaking of an emergent O(4) symmetry, manifesting in a unique excitation spectrum with three gapless Goldstone modes.
  • This phase is characterized by a hidden composite order parameter indicating maximal local entanglement between spin and layer degrees of freedom.

Main claims

  • The system exhibits a novel spin-layer-entangled (SLE) phase with hidden composite order arising from spontaneous breaking of an emergent O(4) symmetry.
    • Evidence: Abstract: 'a novel maximal spin-layer entangled phase… arises from an emergent O(4) symmetry that is spontaneously broken to O(3)'
  • The SLE phase displays three gapless Goldstone modes that are entangled, unlike conventional phases where spin and layer excitations are decoupled.
    • Evidence: Abstract: 'its excitation spectrum features three gapless Goldstone modes that are entangled'

Workflow

  • Model derivation — Coupling between electron spin and layer pseudospin
    • Materials: Two-orbital bilayer Hubbard model
    • Methods: Molecular orbital basis for dz2 orbitals; Schrieffer-Wolff transformation
    • Observations: Low-energy effective Kugel-Khomskii Hamiltonian
  • Ground state analysis — SLE phase has emergent O(4) symmetry and three gapless Goldstone modes
    • Materials: Effective Hamiltonian
    • Methods: Weiss mean-field theory; Generalized flavor-wave theory
    • Observations: Four distinct phases including spin-layer-entangled (SLE) phase