Source capture
Authors Cui-Qun Chen, Ming Zhang, Fan Yang, Dao-Xin Yao
arXiv / Publisher http://arxiv.org/abs/2604.21533v1
PDF https://arxiv.org/pdf/2604.21533v1
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Research paradigm Theoretical
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Summary

Using density functional theory combined with dynamical mean-field theory (DFT+DMFT) and the random phase approximation (RPA), we systematically investigated the electronic structure and superconducting mechanism of the 1313-phase La3Ni2O7. DMFT calculations reveal that the monolayer subsystem exhibits a nearly insulating state, with the dz2 orbital displaying Mott physics, while the trilayer subsystem remains metallic and is primarily responsible for superconductivity, with its Ni-e_g orbitals being hole-doped relative to bulk La4Ni3O10. Based on the low-energy effective Hamiltonian derived from DMFT, RPA analysis yields an s±-wave pairing symmetry within the trilayer subsystem. Compared to bulk La4Ni3O10, the significantly reduced superconducting transition temperature in the 1313 phase arises from two factors: first, hole doping weakens the pairing strength; second, the monolayer subsystem acts as a weak-link layer, forming S-N-S Josephson junctions between adjacent trilayer superconducting layers, which suppresses interlayer phase coherence and further lowers the global transition temperature. Overall, the high-temperature superconductivity in the Ruddlesden-Popper La3Ni2O7 family should be attributed to the 2222 phase rather than the 1313 phase.

Materials

Methods

Keywords

Highlights

  • Establishes that the high-Tc phase in the La3Ni2O7 family is the 2222 bilayer structure, not the 1313 phase.
  • The S-N-S Josephson junction model explains suppressed phase coherence in hybrid phases.

Conclusions

  • The single-layer subsystem in 1313La3Ni2O7 exhibits nearly insulating behavior with Mott physics for the d_z2 orbital, while the trilayer subsystem remains metallic and hosts superconductivity with s± pairing.
  • The reduced Tc compared to bulk La4Ni3O10 is due to hole doping in the trilayer subsystem and weak interlayer Josephson coupling across the single-layer spacer.

Main claims

  • The monolayer subsystem exhibits nearly insulating behavior with the 3d_z2 orbital showing Mott physics, while the trilayer subsystem remains metallic and is primarily responsible for superconductivity.
    • Evidence: DMFT calculations reveal that the monolayer subsystem exhibits a nearly insulating state, with the d_z2 orbital displaying Mott physics, while the trilayer subsystem remains metallic and is primarily responsible for superconductivity
  • RPA analysis yields an s±-wave pairing symmetry within the trilayer subsystem.
    • Evidence: Based on the low-energy effective Hamiltonian derived from DMFT, RPA analysis yields an s±-wave pairing symmetry within the trilayer subsystem.
  • The significantly reduced Tc in 1313 phase arises from hole doping weakening pairing strength and the monolayer subsystem acting as weak-link layers forming S-N-S Josephson junctions, suppressing interlayer phase coherence.
    • Evidence: the significantly reduced superconducting transition temperature in the 1313 phase arises from two factors: first, hole doping weakens the pairing strength; second, the monolayer subsystem acts as a weak-link layer, forming S-N-S Josephson junctions between adjacent trilayer superconducting layers, which suppresses interlayer phase coherence and further lowers the global transition temperature.

Workflow

  • DFT+DMFT calculation — SC primarily resides in the TL subsystem; SL subsystem is a nearly insulating bad metal.
    • Materials: 1313 phase La3Ni2O7 at 20 GPa
    • Methods: density functional theory plus dynamical mean-field theory (DFT+DMFT)
    • Observations: pronounced band renormalization; SL subsystem: nearly insulating bad metal, 3d_z2 orbital shows Mott physics; TL subsystem: metallic, holes doped relative to bulk La4Ni3O10
  • effective model construction — Renormalized model captures low-energy physics with s± pairing tendency.
    • Materials: TL subsystem of 1313La3Ni2O7
    • Methods: tight-binding model derived from DFT+DMFT
    • Observations: renormalized bandwidth 2.1 eV; interlayer hopping reduced; Fermi surface consists of multiple pockets
  • RPA analysis of superconductivity — The TL subsystem exhibits s±-wave pairing symmetry.
    • Materials: effective TL two-orbital model
    • Methods: random phase approximation (RPA)
    • Observations: spin susceptibility dominated by nesting between α and β pockets; leading pairing instability in s±-wave channel
  • analysis of Tc suppression — Two factors suppress Tc: hole doping in TL and weak Josephson coupling between TL subsystems.
    • Materials: 1313La3Ni2O7 compared to bulk La4Ni3O10
    • Methods: comparison of doping and Josephson coupling
    • Observations: hole doping reduces pairing strength; weak intertrilayer hopping leads to S-N-S Josephson junction