Excitonic Phase Transition in Electronic Systems

Although predicted theoretically excitonic phase transitions have never been observed. Recently it has been claimed that they can occur in some strongly correlated materials. We study the possibility of an excitonic transition in a two-band model and show that a true phase transition never occurs in the presence of hybridization. We suggest an alternative interpretation for these experiments based on the opening or closing of a hybridization gap at a critical pressure.