Electron vs. hole doping in infinite-layer nickelates: electronic structure, magnetism and correlations

摘要

通过结合密度泛函理论和动力学平均场理论，研究了无限层镍酸盐LaNiO₂在电子掺杂和空穴掺杂下电子结构、磁性与关联效应的演化。结果显示，由于稀土5d态的存在，Ni-dx²-y²带的自掺杂效应呈现显著不对称：空穴掺杂强烈抑制自掺杂，而电子掺杂虽增大稀土5d电子口袋尺寸，却未有效空穴掺杂Ni-dx²-y²带。这一差异直接影响磁性响应——空穴掺杂迅速压制反铁磁序，电子掺杂则使反铁磁态保持为基态。尽管存在这些差异，两种掺杂下的电子关联均由Ni-dx²-y²轨道主导，表明单带描述在电子和空穴掺杂区均可能适用。

材料

• LaNiO₂
• SrNiO₂
• CeNiO₂
• La_1-xCe_xNiO₂

方法

• DFT
• DMFT
• VCA
• LDA+U

关键词

• self doping asymmetry
• antiferromagnetism
• electronic correlations
• single band description
• magnetic response asymmetry

亮点

• Striking asymmetry in self-doping of Ni-dx2-y2 band due to R(5d) states: suppressed upon hole doping, increased electron pockets but no effective hole-doping upon electron doping.
• Antiferromagnetism rapidly suppressed upon hole doping, remains ground state upon electron doping.
• Electronic correlations dominated by Ni dx2-y2 orbital, suggesting single-band description for both doping regimes.

结论

• There is a clear asymmetry in the electronic structure and magnetic properties upon electron and hole doping in infinite-layer nickelates.
• Electron doping increases the size of the self-doping electron pockets from R(5d) states, but does not effectively hole-dope the Ni-dx2-y2 band.
• Antiferromagnetism is rapidly suppressed upon hole doping, whereas it remains the ground state upon electron doping.
• Electronic correlations in both doping regimes are dominated by the Ni dx2-y2 orbital, suggesting a single-band description may be appropriate.

主要论断

• There is a striking asymmetry in the self-doping of the Ni-dx²-y² band: hole doping strongly suppresses self-doping, while electron doping increases the size of rare-earth 5d electron pockets but does not effectively hole-dope the Ni-d band.
  • 证据: Abstract: 'We find a striking asymmetry in the self-doping of the Ni-dx2-y2 band… while this effect is strongly suppressed upon hole doping, electron doping instead leads to an increase in the size of the R(5d) electron pockets, but without effectively hole-doping the Ni-dx2-y2 band.',Results: 'Importantly, having larger electron pockets in the electron-doped side, does not effectively self-hole-dope the Ni-d band with respect to half-filling.'
• Antiferromagnetism is rapidly suppressed upon hole doping, whereas it remains the ground state upon electron doping.
  • 证据: Abstract: 'antiferromagnetism is rapidly suppressed upon hole doping, whereas it remains the ground state upon electron doping.',Results: 'There is a clear asymmetry as antiferromagnetism is quickly suppressed upon hole doping, while it remains the ground state for electron doping.'
• Electronic correlations on both sides of the phase diagram are dominated by the Ni dx²-y² orbital, suggesting that a single-band description may be appropriate for infinite-layer nickelates in both electron- and hole-doped regimes.
  • 证据: Abstract: 'electronic correlations on both sides of the phase diagram are dominated by the Ni dx2-y2 orbital, suggesting that a single-band description may be appropriate…',Conclusions: 'the low-energy correlation physics of infinite-layer nickelates lives on a single Ni- orbital that is weakly coupled to the charge-reservoirs.'

研究流程

• Structural optimization — Structural models for doped systems were prepared, enabling subsequent electronic structure calculations.
  • 材料: LaNiO₂ supercells with Sr (hole doping) and Ce (electron doping)
  • 方法: VASP code with PAW approach and PBE functional; Virtual crystal approximation (VCA)
  • 观察: Optimized lattice parameters for LaNiO₂, SrNiO₂, and CeNiO₂
• Nonmagnetic DFT electronic structure — Discovered striking asymmetry in self-doping: hole doping suppresses self-doping while electron doping increases pocket size without effectively hole-doping the Ni-d band.
  • 材料: Same doped LaNiO₂ systems
  • 方法: WIEN₂k all-electron full-potential code with FP-APW+lo basis; GGA-PBE exchange-correlation functional
  • 观察: Band structure, density of states, and Fermi surface; Ni-dx²-y² band crossing Fermi level; La-5d electron pockets at A and Γ points; Self-doping effect
• Magnetic properties via spin-polarized DFT+U — Antiferromagnetism is rapidly suppressed upon hole doping, while it remains the ground state upon electron doping.
  • 材料: Same doped LaNiO₂ systems
  • 方法: LDA+U within fully localized limit; U values from 0 to 6 eV, Hund's J=0.8 eV
  • 观察: Energy differences relative to nonmagnetic state; Ni magnetic moment evolution; Spin-polarized density of states
• Dynamical correlations via DFT+DMFT — Electronic correlations are dominated by the Ni-dx²-y² orbital; a single-band description may be appropriate for both doping regimes.
  • 材料: Same doped LaNiO₂ systems (VCA)
  • 方法: TRIQS software with continuous-time quantum Monte Carlo impurity solver (hybridization expansion); Kanamori parametrization (U=4 eV, J=0.8 eV); Held's double counting scheme
  • 观察: Momentum-resolved spectral functions and Fermi surfaces; Orbital-resolved self-energies and mass enhancements