Enhanced s^±-wave superconductivity in electron-doped La₃Ni₂O₇

Summary

Using first-principles calculations and large-scale dynamic cluster quantum Monte Carlo simulations, this work systematically investigates the effect of electron doping on the superconducting properties of two-orbital bilayer models for three representative systems: bulk La₃Ni₂O₇ under ambient pressure and at 15 GPa, as well as the La₃Ni₂O₇:La₃Al₂O₇ heterostructure. The results show that electron doping universally enhances s±-wave pairing superconductivity, with the heterostructure exhibiting the highest superconducting transition temperature in the underdoped region, even exceeding that of bulk samples under 15 GPa pressure. Further analysis reveals an inter-orbital synergistic mechanism: pairing on the dz² orbital induces pairing on the dx²-y² orbital, which gradually dominates at low temperatures, forming a two-orbital collaborative superconducting instability. This conclusion is validated by simulations with two different cluster sizes. This study provides a theoretical prediction for enhanced superconductivity in electron-doped Ruddlesden-Popper phase nickelates and proposes the heterostructure as a feasible experimental pathway, awaiting future experimental verification.

Materials

• La₃Ni₂O₇
• La₃Ni₂O₇:La₃Al₂O₇ heterostructure

Methods

• First-principles DFT calculations
• Dynamical cluster quantum Monte Carlo (DCA-QMC)
• Bethe-Salpeter equation

Keywords

• electron doping
• s± wave pairing
• dome like phase diagram
• inter orbital cooperative mechanism
• hund's coupling
• heterostructure

Highlights

• First theoretical prediction of enhanced superconductivity in electron-doped RP nickelates.
• Proposes a concrete and experimentally feasible heterostructure design to realize electron doping and enhanced T_c.

Conclusions

• Electron doping universally enhances s±-wave pairing superconductivity in all three cases: bulk La₃Ni₂O₇ at 0 GPa, at 15 GPa, and the La₃Ni₂O₇:La₃Al₂O₇ heterostructure.
• The heterostructure shows the highest T_c in the underdoped regime, even exceeding that of pressurized bulk.
• An inter-orbital cooperative mechanism is suggested: pairing on the dx2-y2 orbital is induced by pairing on the dz2 orbital, with the dx2-y2 pairing gradually dominating at low temperatures.

Main claims

• Electron doping universally enhances s±-wave pairing superconductivity in La₃Ni₂O₇ systems
  • Evidence: From abstract: 'electron doping generically enhances s±-wave pairing superconductivity (SC) in all three cases'
• Inter-orbital cooperative mechanism: pairing on dx2-y2 orbital induced by that on dz2 orbital
  • Evidence: From abstract: 'inter-orbital cooperative mechanism that the pairing on the dx2-y2 orbital, induced by that on the dz2 orbital, plays a vital role'

Workflow

• model_construction — Constructed effective model for La₃Ni₂O₇ systems
  • Materials: Ni-3d orbitals; O-2p orbitals
  • Methods: two-orbital bilayer tight-binding model
  • Observations: band structure; Fermi surface
• first_principles_calculations — Obtained accurate tight-binding parameters
  • Materials: Bulk La₃Ni₂O₇; Heterostructure La₃Ni₂O₇:La₃Al₂O₇
  • Methods: density functional theory (DFT)
  • Observations: hopping parameters; band structure
• quantum_monte_carlo_simulations — Electron doping enhances s±-wave pairing
  • Materials: Two-orbital bilayer model
  • Methods: dynamical cluster approximation (DCA); continuous-time quantum Monte Carlo (CT-QMC)
  • Observations: pairing eigenvalues; pair-field susceptibility