Os efeitos da hibridização no crossover BCS-BEC com interações interbandas

Abstract

In this work we discuss the behavior of a superconducting system described by a multiband model, so it is an extension of the BCS theory which describes well the low temperature superconductors. We consider the interbanding interaction, that is, the interaction between fermions that present different properties under the influence of hybridization, evaluating the crossover between the weak coupling (BCS) and the strong coupling (BEC) for symmetry type s Order parameter in T = 0 and in the presence of a hybridization. However, the objective of this work is to study superconductivity without a two-band model, with interband interactions, with the purpose of obtaining as equations for the superconducting Gaps and, concomitantly, to evaluate a development of the systems between the limit of weak couplings (BCS) and strong couplings (BEC) and estimate an influence that is a hybridization on the system. Using Zubarev's Green function method, we calculate interband superconducting order parameters and chemical potential as a function of the interaction 1/kpa, in order to obtain a complete study of the system. We explore the energies of excitation at the two limits of the coupling, considering their characteristics and we see that there is a discontinuity in the amplitude of the interband gap. Our results suggest that hybridization V acts at the expense of superconductivity, suppressing it, agreeing with other works, although this is not general, since some works show that V contributes to superconductivity up to a certain value and to other values, destroys it. We also notice that in interband interaction we have first and second order transitions and a tricritic point, in which We have the encounter of a first order line with a second order line.