Bound state formation and the nature of the excitonic insulator phase in the extended Falicov-Kimball model

Ihle, D and Pfafferott, M and Burovski, Evgeni and Bronold, F.X. and Fehske, H (2008) Bound state formation and the nature of the excitonic insulator phase in the extended Falicov-Kimball model. Physical review B, 78 (19). ISSN 1098-0121

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Abstract

Motivated by the possibility of pressure-induced exciton condensation in intermediate-valence Tm[Se,Te] compounds, we study the Falicov-Kimball model extended by a finite f-hole valence bandwidth. Calculating the Frenkel-type exciton propagator we obtain excitonic bound states above a characteristic value of the local interband Coulomb attraction. Depending on the system parameters coherence between c and f states may be established at low temperatures, leading to an excitonic insulator phase. We find strong evidence that the excitonic insulator typifies either a BCS condensate of electron-hole pairs (weak-coupling regime) or a Bose-Einstein condensate (BEC) of preformed excitons (strong-coupling regime), which points toward a BCS-BEC transition scenario as Coulomb correlations increase.

Item Type:
Journal Article
Journal or Publication Title:
Physical review B
ID Code:
61736
Deposited By:
Deposited On:
06 Feb 2013 17:43
Refereed?:
Yes
Published?:
Published
Last Modified:
18 Nov 2020 11:59