Hybridization-gap formation and superconductivity in the pressure-induced semimetallic phase of the excitonic insulator Ta2NiSe5

Kazuyuki Matsubayashi, Hidekazu Okamura, Takashi Mizokawa, Naoyuki Katayama, Akitoshi Nakano, Hiroshi Sawa, Tatsuya Kaneko, Tatsuya Toriyama, Takehisa Konishi, Yukinori Ohta, Hiroto Arima, Rina Yamanaka, Akihiko Hisada, Taku Okada, Yuka Ikemoto, Taro Moriwaki, Koji Munakata, Akiko Nakao, Minoru Nohara, Yangfan LuHidenori Takagi, Yoshiya Uwatoko

Research output: Contribution to journalArticlepeer-review

Abstract

The excitonic insulator Ta2NiSe5 experiences a first-order structural transition under pressure from rippled to flat layer-structure at Ps ~ 3 GPa, which drives the system from an almost zero-gap semiconductor to a semimetal. The pressure-induced semimetal, with lowering temperature, experiences a transition to another semimetal with a partial-gap of ~0.1-0.2 eV, accompanied with a monoclinic distortion analogous to that occurs at the excitonic transition below Ps. We argue that the partial-gap originates primarily from a symmetry-allowed hybridization of Ta-conduction and Nivalence bands due to the lattice distortion, indicative of the importance of electron-lattice coupling. The transition is suppressed with increasing pressure to Pc ~ 8 GPa. Superconductivity with a maximum Tsc ~ 1.2K emerges around Pc, likely mediated by strongly electron-coupled soft phonons. The electron-lattice coupling is as important ingredient as the excitonic instability in Ta2NiSe5.

Original languageEnglish
Article number074706
Journaljournal of the physical society of japan
Volume90
Issue number7
DOIs
Publication statusPublished - 2021 Jul 1

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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