Source capture
Authors Y. Shen, W. He, J. Sears, Xuefei Guo, Xiangpeng Luo, A. Roll, J. Li, J. Pelliciari, Xi He, I. Bozovic, Junjie Zhang, J. F. Mitchell, V. Bisogni, M. Mitrano, S. Johnston, M. P. M. Dean
arXiv / Publisher http://arxiv.org/abs/2601.12160v1
PDF https://arxiv.org/pdf/2601.12160v1
Relevance score 4.943
Primary category cond-mat.str-el
Published 2026-06-16
Research paradigm Experimental
Sample form Single Crystal

Summary

Using resonant inelastic X-ray scattering (RIXS) at the oxygen K-edge, plasmon collective excitations were observed in the low-valence nickelate Pr4Ni3O8 and compared with the overdoped cuprate La2-xSrxCuO4. The experiments revealed that the nickelate plasmons exhibit dispersive behavior within the in-plane momentum, but with significantly lower velocity and stronger damping than the cuprate, and they become overdamped and disappear at much smaller momenta. Random phase approximation (RPA) calculations indicate that these differences originate from reduced electron hopping and enhanced long-range Coulomb interaction screening in the nickelate, where both the in-plane hopping integral and Coulomb interaction strength are substantially smaller than in the cuprate. Furthermore, the out-of-plane plasmons in the nickelate showed no discernible dispersion, possibly due to its trilayer coupling structure. Temperature-dependent studies found that the plasmons in Pr4Ni3O8 soften with increasing temperature, whereas in the cuprate the energy remains nearly constant while damping increases, suggesting the presence of additional correlations such as stripe fluctuations in the nickelate. These results reveal a unique charge screening landscape in nickelates, where weakened electron hopping and enhanced Coulomb screening are key distinguishing features from cuprates, potentially explaining the lower superconducting transition temperature of nickelates and providing quantitative experimental constraints for analogies between the two material families.

Materials

Methods

Keywords

  • plasmons
  • charge dynamics
  • screened coulomb interactions
  • electron hopping
  • stripe fluctuations

Highlights

  • Our findings establish reduced electronic hopping and smaller, more strongly screened, long-range Coulomb interactions as defining features differentiating low-valence nickelates from cuprates.
  • These results may explain the lower superconducting transition temperature of low-valence nickelates compared to cuprates.

Conclusions

  • The nickelate plasmons are more heavily damped and have a lower velocity than those in a cuprate at comparable doping.
  • The plasmons in Pr4Ni3O8 soften with increasing temperature, in contrast to the cuprate where they remain at nearly fixed energy but become more strongly damped.
  • Reduced electronic hopping and enhanced screening of long-range Coulomb interactions are attributed as the cause.

Main claims

  • Plasmons in Pr4Ni3O8 have lower velocity and are more heavily damped than in overdoped La2-xSrxCuO4, disappearing at smaller momenta.
    • Evidence: Abstract: 'The experiments revealed that the nickelate plasmons exhibit dispersive behavior… but with significantly lower velocity and stronger damping than the cuprate'
  • RPA calculations attribute these differences to reduced electronic hopping and enhanced long-range Coulomb interaction screening in the nickelate.
    • Evidence: Abstract: 'Random phase approximation calculations indicate that these differences originate from reduced electron hopping and enhanced long-range Coulomb interaction screening'

Workflow

  • Sample synthesis
    • Materials: Pr4Ni3O8 single crystals; La2-xSrxCuO4 thin films
    • Methods: High-pressure optical floating zone method; Topotactic reduction in H2/Ar; Atomic-layer-by-layer MBE for cuprate
    • Observations: High-quality crystals with Ni valence state ~+1.33
  • RIXS measurements — Plasmons in nickelates are more heavily damped and have lower velocity than in cuprates
    • Materials: Pr4Ni3O8 and La2-xSrxCuO4
    • Methods: O K-edge resonant inelastic X-ray scattering; Polarization analysis
    • Observations: Well-defined dispersive plasmons below 1 eV; Nickelate plasmons have lower velocity and stronger damping
  • Theoretical modeling — Differences originate from reduced electron hopping and enhanced Coulomb screening
    • Materials: Experimental plasmon dispersion
    • Methods: Random phase approximation (RPA) calculations; Single-layer and trilayer models
    • Observations: Reduced in-plane hopping and long-range Coulomb interaction in nickelate