BCS model in Tsallis' statistical framework

We show that there is an effect of nonextensivity acting upon the BCS model for superconductors in the ground state that motivates its study in the Ts allis' statistical framework. We show that the weak-coupling limit supercon ductors are well described by q similar to1, where q is a real parameter wh ich characterizes the degree of nonextensivity of the Tsallis' entropy. Nev ertheless, small deviations with respect to q=1 provide better agreement wh en compared with experimental results. To illustrate this point, making use of an approximated Fermi function, we show that measurements of the specif ic heat, ultrasonic attenuation and tunneling experiments for tin (Sn) are better described with q = 0.99. (C) 2001 Elsevier Science B.V. All rights r eserved.