2013/08/31 by Satoshi Ejima, S. Ejima, Tatsuya Kaneko +4 · 56 citations
Engineering · Physics and Astronomy · #Bound state #Condensed matter physics #Coulomb #Electron #Exciton #Hubbard model #Pairing #Perovskite Materials and Applications #Phase (matter) #Phase diagram #Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Quantum mechanics #Quasiparticle #Superconductivity #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.112.026401
published in Physical Review Letters 112(2), 026401 (American Physical Society) · 5 pages, 4 figures, final version
openalex publication_date 2014/01/13 · arxiv created 2014/01/14 · arxiv updated 2014/01/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Using exact numerical techniques, we investigate the nature of excitonic (electron-hole) bound states and the development of exciton coherence in the one-dimensional half-filled extended Falicov-Kimball model. The ground-state phase diagram of the model exhibits, besides band-insulator and staggered orbital ordered phases, an excitonic insulator (EI) with power-law correlations. The criticality of the EI state shows up in the von Neumann entropy. The anomalous spectral function and condensation amplitude provide the binding energy and coherence length of the electron-hole pairs which, on their part, point towards a Coulomb interaction driven crossover from BCS-like electron-hole pairing fluctuations to tightly bound excitons. We show that while a mass imbalance between electrons and holes does not affect the location of the BCS-BEC crossover regime, it favors staggered orbital ordering to the disadvantage of the EI. Within the Bose-Einstein condensation (BEC) regime, the quasiparticle dispersion develops a flat valence-band top, in accord with the experimental finding for Ta2NiSe5.