Role of intraband and interband pairings in two-band superconductors: deviation from BCS results

We study the stability of the intraband (r = dd) and interband (r = sd) cou plings in the presence of the k-dependent hybridization in a two-band syste m. We calculate the critical temperature T-c,T-r associated to both type of couplings, and we verified that there is a critical value of the hybridiza tion V-c, for which T-c,T-r vanishes. Then we obtain the value of epsilon ( r) = 2 Delta (r)*(0)/k(B) T-c,T-r and the isotope coefficients gamma (r) sh owing that under some circumstances. one can obtain values for epsilon (r) and gamma (r) which differ considerably from standard BCS results for both Cooper pairings. (C) 2001 Published by Elsevier Science B.V.