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

doi:10.1103/PhysRevB.100.245129

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

Research output: Contribution to journal › Article › peer-review

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 language	English
Article number	245129
Journal	Physical Review B
Volume	10
Issue number	24
DOIs	https://doi.org/10.1103/PhysRevB.100.245129
Publication status	Published - 2019 Dec 18
Externally published	Yes

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

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@article{7275e65993b64fc794820c59d688bc54,

title = "Valence-bond insulator in proximity to excitonic instability",

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.",

author = "Y. Chiba and T. Mitsuoka and Saini, {N. L.} and K. Horiba and M. Kobayashi and K. Ono and H. Kumigashira and N. Katayama and H. Sawa and M. Nohara and Lu, {Y. F.} and H. Takagi and T. Mizokawa",

note = "Funding Information: The authors would like to thank Prof. H. Fukuyama, Prof. Y. Ohta, and Prof. C. Monney for the valuable discussions and Dr. Y. Wakisaka and Dr. D. Ootsuki for the contributions at the early stage of this work. This work was partially supported by Grants-in-Aid from the Japan Society of the Promotion of Science (JSPS) (Grant No. 19H00659) and CREST (Grant No. JPMJCR15Q2) from the Japan Science and Technology Agency (JST). The synchrotron radiation experiment was performed with the approval of Photon Factory, KEK (Grant No. 2015G058). This work was supported by joint research program of ZAIKEN, Waseda University (Project No. 31010). ",

year = "2019",

month = dec,

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doi = "10.1103/PhysRevB.100.245129",

language = "English",

volume = "10",

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TY - JOUR

T1 - Valence-bond insulator in proximity to excitonic instability

AU - Chiba, Y.

AU - Mitsuoka, T.

AU - Saini, N. L.

AU - Horiba, K.

AU - Kobayashi, M.

AU - Ono, K.

AU - Kumigashira, H.

AU - Katayama, N.

AU - Sawa, H.

AU - Nohara, M.

AU - Lu, Y. F.

AU - Takagi, H.

AU - Mizokawa, T.

N1 - Funding Information: The authors would like to thank Prof. H. Fukuyama, Prof. Y. Ohta, and Prof. C. Monney for the valuable discussions and Dr. Y. Wakisaka and Dr. D. Ootsuki for the contributions at the early stage of this work. This work was partially supported by Grants-in-Aid from the Japan Society of the Promotion of Science (JSPS) (Grant No. 19H00659) and CREST (Grant No. JPMJCR15Q2) from the Japan Science and Technology Agency (JST). The synchrotron radiation experiment was performed with the approval of Photon Factory, KEK (Grant No. 2015G058). This work was supported by joint research program of ZAIKEN, Waseda University (Project No. 31010).

PY - 2019/12/18

Y1 - 2019/12/18

N2 - 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.

AB - 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.

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