1211.4735 (Apinyan V. A. et al.)

The phase coherence and pseudogap at the excitonic phase transition in a
three-dimensional extended Falicov-Kimball model    [PDF]

Apinyan V. A., Kopeć T. K

Considering the phase coherence mechanism between the conduction band electrons and valence band holes we derive the excitonic phase stiffness for the three-dimensional strongly correlated electron system. It is shown that the phase coherence between the conduction and valence bands is important for the excitonic condensation at the very low temperatures. We prove that the Bose-superfluid excitonic transition critical lines driven by the phase stiffness in the strong and intermediate coupling regimes differ considerably from the excitonic pair formation temperature transition lines. The true condensate transition temperature appears to be much smaller than the exciton pair formation transition temperature. We show that a BEC to BCS type crossover could be expected in our model. In the strong interaction case the system is driven into the insulator state with a BEC condensation at the very low temperatures, while in the small interaction region the condensate order is governed by the pair formation and in this case the system is evidently in the BCS-like regime.

View original: http://arxiv.org/abs/1211.4735