Physical Review X (Jan 2022)

CaCu_{3}Ru_{4}O_{12}: A High-Kondo-Temperature Transition-Metal Oxide

  • D. Takegami,
  • C.-Y. Kuo,
  • K. Kasebayashi,
  • J.-G. Kim,
  • C. F. Chang,
  • C. E. Liu,
  • C. N. Wu,
  • D. Kasinathan,
  • S. G. Altendorf,
  • K. Hoefer,
  • F. Meneghin,
  • A. Marino,
  • Y. F. Liao,
  • K. D. Tsuei,
  • C. T. Chen,
  • K.-T. Ko,
  • A. Günther,
  • S. G. Ebbinghaus,
  • J. W. Seo,
  • D. H. Lee,
  • G. Ryu,
  • A. C. Komarek,
  • S. Sugano,
  • Y. Shimakawa,
  • A. Tanaka,
  • T. Mizokawa,
  • J. Kuneš,
  • L. H. Tjeng,
  • A. Hariki

DOI
https://doi.org/10.1103/PhysRevX.12.011017
Journal volume & issue
Vol. 12, no. 1
p. 011017

Abstract

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We present a comprehensive study of CaCu_{3}Ru_{4}O_{12} using bulk sensitive hard and soft x-ray spectroscopy combined with local-density approximation+dynamical mean-field theory (DMFT) calculations. Correlation effects on both the Cu and Ru ions can be observed. From the Cu 2p core-level spectra, we deduce the presence of magnetic Cu^{2+} ions hybridized with a reservoir of itinerant electrons. The strong photon energy dependence of the valence band allows us to disentangle the Ru, Cu, and O contributions and, thus, to optimize the DMFT calculations. The calculated spin and charge susceptibilities show that the transition metal oxide CaCu_{3}Ru_{4}O_{12} must be classified as a Kondo system and that the Kondo temperature is in the range of 500–1000 K.