Jj. Rodriguez-nunez et Aa. Schmidt, Superconducting critical temperature, for s-wave symmetry order parameter,for intermediate correlated electron systems, PHYSICA C, 350(1-2), 2001, pp. 88-96
We calculate the superconducting critical temperature, T-c, for an s-wave o
rder parameter, in the presence of local Coulomb interactions by using a no
rmal state one particle Green function, G(N)((k) over right arrow ,i omega
(n)), which is renormalized by the interactions. In the end, we adopt for G
(N)((k) over right arrow ,i omega (n)) a Hubbard-III like approximation sin
ce it can give a normal metal-insulator transition and as such can be used
to study T-c vs. U for intermediate values of U, going beyond the mean-fiel
d treatment for the local Coulomb interaction, U. However, the equation for
T-c is mean-field like with respect to the pairing interaction, V, which w
e assume with a different origin than the repulsive part. We have calculate
d. (1) T-c vs. U for different values of V and chemical potential, mu; (2)
T-c vs. rho dropn/2 for different values of V and U. The conclusions we rea
ch are: (a) the local Coulomb interaction is always detrimental to supercon
ductivity, namely, T-c goes down with increasing U; (b) the maximum value o
f T-c is reached away from half-filling, contrary to the pure BCS-case (U d
rop 0). Results (a) have also been obtained in non-Fermi liquid theories. W
e have compared our results with known relevant work. (C) 2001 EIsevier Sci
ence B.V. All rights reserved.