Weak-Coupling Theory for Multiband Superconductivity Induced by Jahn-Teller Phonons

Emergence of superconductivity in a two-band system coupled with breathing and Jahn-Teller phonons is discussed in a weak-coupling limit. With the use of a standard quantum Mechanical procedure, the Phonon-mediated attraction is derived. From the analysis of the model including Such attraction, a BCS-like formula for a superconducting transition temperature T-c is obtained. When only the breathing phonon is considered T-c is the same as that of the one-band model. On the Other hand, when Jahn-Teller phonons are active, T-c is significantly enhanced by the interband attraction even within the weak-coupling limit. Relevance of the present result to actual materials Such as iron pnictides is briefly commented.