Strong Coupling Nature of the Excitonic Insulator State in Ta${}_2$NiSe${}_5$

Abstract

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 Ta${}_2$NiSe${}_5$, 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.

5 pages, 4 figures, Supplemental Material

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• Implementation of screened hybrid functionals based on the Yukawa potential within the LAPW basis set
• Excitonic Bose-Einstein condensation in Ta2NiSe5 above room temperature
• On the possibility of an excitonic insulator at the semiconductor-semimetal transition
• Photo-induced enhancement of excitonic order
• Density-matrix renormalisation group approach to quantum impurity problems
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Cited by in corpus (51)

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• FFLO Superconductivity Mediated by Excitonic Fluctuation in Semimetallic Ta${}_2$NiSe${}_5$
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• Photoinduced dynamics of excitonic order and Rabi oscillation in the two-orbital Hubbard model
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