We present a comprehensive study of CaCu3Ru4O12 using bulk sensitive hard and soft x-ray spectroscopy combined with local-density approximation (LDA) + 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 Cu2+ 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 CaCu3Ru4O12 must be classified as a Kondo system and that the Kondo temperature is in the range of 500-1000 K.
@article{arxiv.2112.02898,
title = {CaCu$_3$Ru$_4$O$_{12}$: a high Kondo-temperature transition metal oxide},
author = {D. Takegami and C. Y. Kuo and K. Kasebayashi and J. -G. Kim and C. F. Chang and C. E. Liu and C. N. Wu and D. Kasinathan and S. G. Altendorf and K. Hoefer and F. Meneghin and A. Marino and Y. F. Liao and K. D. Tsuei and C. T. Chen and K. -T. Ko and A. Günther and S. G. Ebbinghaus and J. W. Seo and D. H. Lee and G. Ryu and A. C. Komarek and S. Sugano and Y. Shimakawa and A. Tanaka and T. Mizokawa and J. Kuneš and L. H. Tjeng and A. Hariki},
journal= {arXiv preprint arXiv:2112.02898},
year = {2023}
}