2018/03/31 by K. Sugimoto, S. Nishimoto, T. Kaneko +1 · 1 citation
Physics and Astronomy · #cond-mat.str-el #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevlett.120.247602
published as Phys. Rev. Lett. 120, 247602 (2018) · 5 pages, 4 figures, Supplemental Material
arxiv created 2018/06/15 · arxiv updated 2018/06/18
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.