Strong Coupling Nature of the Excitonic Insulator State in Ta2NiSe5

Koudai Sugimoto, Satoshi Nishimoto, Tatsuya Kaneko, Yukinori Ohta

Research output: Contribution to journalArticlepeer-review

69 Citations (Scopus)


We analyze the measured optical conductivity spectra using the density-functional-theory-based electronic structure calculation and density-matrix renormalization group calculation of an effective model. We show that, in contrast to a conventional description, the Bose-Einstein condensation of preformed excitons occurs in Ta2NiSe5, despite the fact that a noninteracting band structure is a band-overlap semimetal rather than a small band-gap semiconductor. The system above the transition temperature is therefore not a semimetal but rather a state of preformed excitons with a finite band gap. A novel insulator state caused by the strong electron-hole attraction is thus established in a real material.

Original languageEnglish
Article number247602
JournalPhysical review letters
Issue number24
Publication statusPublished - 2018 Jun 14
Externally publishedYes

ASJC Scopus subject areas

  • General Physics and Astronomy


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