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

摘要

通过第一性原理计算和大规模动态簇量子蒙特卡洛模拟，该工作系统研究了电子掺杂对三种代表性体系（常压与15 GPa下的块体La₃Ni₂O₇，以及异质结La₃Ni₂O₇:La₃Al₂O₇）的双轨道双层模型超导性质的影响。结果表明，电子掺杂普遍增强了s±波配对超导，其中异质结在欠掺杂区表现出最高的超导转变温度，甚至超过15 GPa加压下的块体样品。进一步分析发现了一种轨道间协同机制：dz²轨道上的配对诱导了dx²-y²轨道上的配对，后者在低温下逐渐占据主导，形成双轨道协作的超导不稳定性。这一结论在两种不同簇尺寸的模拟中均得到验证。该研究为电子掺杂Ruddlesden-Popper相镍酸盐中增强超导性提供了理论预测，并提出了异质结这一可行的实验实现路径，期待未来实验验证。

材料

• La₃Ni₂O₇
• La₃Ni₂O₇:La₃Al₂O₇ heterostructure

方法

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

关键词

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

亮点

• 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.

结论

• 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.

主要论断

• Electron doping universally enhances s±-wave pairing superconductivity in La₃Ni₂O₇ systems
  • 证据: 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
  • 证据: 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'

研究流程

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