Valence-bond insulator in proximity to excitonic instability

被引：10

作者：

Chiba, Y. ^{[1
]}

Mitsuoka, T. ^{[2
]}

Saini, N. L. ^{[3
]}

Horiba, K. ^{[4
]}

Kobayashi, M. ^{[4
]}

Ono, K. ^{[4
]}

Kumigashira, H. ^{[4
]}

Katayama, N. ^{[5
]}

Sawa, H. ^{[5
]}

Nohara, M. ^{[6
]}

Lu, Y. F. ^{[7
]}

Takagi, H. ^{[7
,8
]}

Mizokawa, T. ^{[2
]}

机构：

[1] Univ Tokyo, Dept Phys, 5-1-5 Kashiwanoha, Chiba 2778561, Japan

[2] Waseda Univ, Dept Appl Phys, Shinjuku Ku, Tokyo 1698555, Japan

[3] Univ Roma La Sapienza, Dept Phys, Piazalle Aldo Moro 2, I-00185 Rome, Italy

[4] High Energy Accelerator Res Org KEK, Inst Mat Struct Sci, Tsukuba, Ibaraki 3050801, Japan

[5] Nagoya Univ, Dept Appl Phys, Nagoya, Aichi 4648603, Japan

[6] Okayama Univ, Res Inst Interdisciplinary Sci, Okayama 7008530, Japan

[7] Univ Tokyo, Dept Phys, Tokyo 1130033, Japan

[8] Mak Planck Inst Solid State Res, D-70569 Stuttgart, Germany

来源：

PHYSICAL REVIEW B | 2019年 / 100卷 / 24期

基金：

日本科学技术振兴机构;

关键词：

TRANSITION; PHOTOEMISSION; CRYSTAL; TA2NIS5; PHASE;

D O I：

10.1103/PhysRevB.100.245129

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

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.

引用

页数：5

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