Valence-bond insulator in proximity to excitonic instability

Y. Chiba, T. Mitsuoka, N. L. Saini, K. Horiba, M. Kobayashi, K. Ono, H. Kumigashira, N. Katayama, H. Sawa, M. Nohara, Y. F. Lu, H. Takagi, T. Mizokawa

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Abstract

Ta2NiS5 is supposed to be a simple semiconductor in which excitonic instability of Ta2NiSe5 is suppressed due to its large band gap. However, the Ni 2p core-level photoemission of Ta2NiS5 exhibits a satellite indicating Ni 3d orbitals are mixed into its conduction band as expected in an excitonic insulator. The valence band does not show dispersion flattening and spectral sharpening which are fingerprints of an excitonic insulator. Instead, Ni 3p-3d resonant photoemission indicates Mottness of the Ni 3d electron in Ta2NiS5 with negative charge-transfer energy. The present results show that Ta2NiS5 can be viewed as a valence bond insulator with a band gap exceeding the exciton binding energy.

Original languageEnglish
Article number245129
JournalPhysical Review B
Volume10
Issue number24
DOIs
Publication statusPublished - Dec 18 2019

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Chiba, Y., Mitsuoka, T., Saini, N. L., Horiba, K., Kobayashi, M., Ono, K., Kumigashira, H., Katayama, N., Sawa, H., Nohara, M., Lu, Y. F., Takagi, H., & Mizokawa, T. (2019). Valence-bond insulator in proximity to excitonic instability. Physical Review B, 10(24), [245129]. https://doi.org/10.1103/PhysRevB.100.245129