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Anomalous charge and negative-charge-transfer insulating state in cuprate chain compound KCuO2

D. Choudhury, P. Rivero, D. Meyers, X. Liu, Y. Cao, S. Middey, M. J. Whitaker, S. Barraza-Lopez, J. W. Freeland, M. Greenblatt, and J. Chakhalian
Phys. Rev. B 92, 201108(R) – Published 19 November 2015
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Abstract

Using a combination of x-ray absorption spectroscopy (XAS) experiments and first-principles calculations, we demonstrate that insulating KCuO2 contains Cu in an unusually high formal 3+ valence state, and the ligand-to-metal (O-to-Cu) charge-transfer energy is intriguingly negative (Δ1.5 eV) and has a dominant (60%) ligand-hole character in the ground state akin to the high Tc cuprate Zhang-Rice state. Unlike most other formal Cu3+ compounds, the Cu 2p XAS spectra of KCuO2 exhibit pronounced 3d8 (Cu3+) multiplet structures, which account for 40% of its ground state wave function. Ab initio calculations elucidate the origin of the band gap in KCuO2 as arising primarily from strong intracluster Cu 3d-O 2p hybridizations (tpd); the value of the band gap decreases with a reduced value of tpd. Further, unlike conventional negative-charge-transfer insulators, the band gap in KCuO2 persists even for vanishing values of Coulomb repulsion U, underscoring the importance of single-particle band-structure effects connected to the one-dimensional nature of the compound.

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  • Received 22 April 2015
  • Revised 3 November 2015

DOI:https://doi.org/10.1103/PhysRevB.92.201108

©2015 American Physical Society

Authors & Affiliations

D. Choudhury1,2,*, P. Rivero1, D. Meyers1, X. Liu1, Y. Cao1, S. Middey1, M. J. Whitaker3, S. Barraza-Lopez1, J. W. Freeland4, M. Greenblatt3, and J. Chakhalian1

  • 1Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
  • 2Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
  • 3Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854-8087, USA
  • 4Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA

  • *debraj@phy.iitkgp.ernet.in

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Vol. 92, Iss. 20 — 15 November 2015

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