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

Summary

B_y combining density functional theory and dynamical mean-field theory, the evolution of the electronic structure, magnetism, and correlation effects in the infinite-layer nickelate LaNiO₂ under electron and hole doping is investigated. The results reveal that, due to the presence of rare-earth 5d states, the self-doping effect of the Ni-dx²-y² band exhibits significant asymmetry: hole doping strongly suppresses self-doping, whereas electron doping, while enlarging the rare-earth 5d electron pocket, does not effectively hole-dope the Ni-dx²-y² band. This difference directly impacts the magnetic response—hole doping rapidly suppresses antiferromagnetic order, while electron doping maintains the antiferromagnetic state as the ground state. Despite these disparities, the electronic correlations in both doping regimes are dominated by the Ni-dx²-y² orbital, suggesting that a single-band description may be applicable in both electron- and hole-doped regions.

Materials

• LaNiO₂
• SrNiO₂
• CeNiO₂
• La_1-xCe_xNiO₂

Methods

• DFT
• DMFT
• VCA
• LDA+U

Keywords

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

Highlights

• 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.

Conclusions

• 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.

Main claims

• 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.
  • Evidence: 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.
  • Evidence: 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.
  • Evidence: 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.'

Workflow

• Structural optimization — Structural models for doped systems were prepared, enabling subsequent electronic structure calculations.
  • Materials: LaNiO₂ supercells with Sr (hole doping) and Ce (electron doping)
  • Methods: VASP code with PAW approach and PBE functional; Virtual crystal approximation (VCA)
  • Observations: 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.
  • Materials: Same doped LaNiO₂ systems
  • Methods: WIEN₂k all-electron full-potential code with FP-APW+lo basis; GGA-PBE exchange-correlation functional
  • Observations: 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.
  • Materials: Same doped LaNiO₂ systems
  • Methods: LDA+U within fully localized limit; U values from 0 to 6 eV, Hund's J=0.8 eV
  • Observations: 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.
  • Materials: Same doped LaNiO₂ systems (VCA)
  • Methods: 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
  • Observations: Momentum-resolved spectral functions and Fermi surfaces; Orbital-resolved self-energies and mass enhancements