Electronic structure of the local-singlet insulator NaCuO2

T. Mizokawa*, A. Fujimori, H. Namatame, K. Akeyama, N. Kosugi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

88 Citations (Scopus)


The insulating oxide NaCuO2 has been studied by x-ray photoemission spectroscopy and subsequent cluster-model analysis. It is found that the d8→d9L charge-transfer energy (L:ligand hole) is negative and the ground state is dominated by the d9L configuration. Using the Anderson impurity model, it is shown that strong 3d-ligand hybridization opens a band gap for a negative charge-transfer energy. This band gap corresponds to charge fluctuations mainly of the p-p type, d9L+d9L→d9+d9L2, with a considerable mixture of d character into the p states, and not of the conventional Mott-Hubbard (d-d) type nor of the charge-transfer (p-d) type. The magnitude of the gap is strongly affected by the geometrical arrangement of metal-oxygen local units, giving a natural explanation for the difference between the insulating NaCuO2 and metallic LaCuO3. The electronic structures of Fe4+ and Ni3+ oxides and their insulating versus metallic behaviors, which are expected to resemble those of the Cu3+ oxides, are also discussed. To generalize the above conclusions, a modification of the metal-insulator boundaries in the Zaanen-Sawatzky-Allen diagram is proposed to include compounds with small or negative charge-transfer energies.

Original languageEnglish
Pages (from-to)7193-7204
Number of pages12
JournalPhysical Review B
Issue number11
Publication statusPublished - 1994
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics


Dive into the research topics of 'Electronic structure of the local-singlet insulator NaCuO2'. Together they form a unique fingerprint.

Cite this