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Electronic coupling in square planar La4Ni3O8.

M H Upton1, Junjie Zhang2,3, Hong Zheng2

  • 1Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, United States of America.

Journal of Physics. Condensed Matter : an Institute of Physics Journal
|July 7, 2020
PubMed
Summary

Resonant inelastic x-ray scattering reveals strong Ni 3d-Ni 4p Coulomb interactions in La4Ni3O8, influencing dd excitations. An insulating gap closes with increasing temperature.

Keywords:
electronic structurenickelateresonant inelastic x-ray scatteringsquare planar

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Area of Science:

  • Condensed Matter Physics
  • Materials Science
  • X-ray Spectroscopy

Background:

  • La4Ni3O8 (La-438) is a material exhibiting complex electronic properties.
  • Understanding electronic excitations is crucial for characterizing materials.

Purpose of the Study:

  • To investigate dd excitations in La-438 using advanced x-ray scattering techniques.
  • To elucidate the underlying physical mechanisms of these excitations.

Main Methods:

  • X-ray absorption scattering and Resonant Inelastic X-ray Scattering (RIXS) at the Nickel (Ni) K-edge.
  • Analysis of incident energy dependence and x-ray polarization effects.

Main Results:

  • dd excitation shows a maximum at the 1s→4pπ transition.
  • Excitation intensity correlates with x-ray polarization parallel to the c-axis.
  • An insulating gap closing was observed with increasing temperature.

Conclusions:

  • The RIXS process involves strong Ni 3d-Ni 4p Coulomb interaction, specifically with Ni 4pπ.
  • The '4p-as-spectator' approximation is not applicable.
  • Temperature-dependent insulating gap closure indicates a phase transition.