Theory of quasi-2D superconducting fluctuation

We examine effects of the quasi-2D superconducting fluctuation of s-wave Co oper pairs in a weak coupling case on self-energy corrections for single pa rticle Green's function and vertex corrections for the Cooper pairing susce ptibility chi (q, omega) by taking account of the most divergent contributi ons to those. We find that, as T decreases at T less than or similar to T-c ((0)), the superconducting fluctuation is evolved significantly and chi (0, 0) diverges as T(-TF/2T)/log\T-F/T\ at T --> 0, which confirms that the 2D -super-conducting fluctuation suppresses the superconducting transition tem perature T,down to zero. In the above, TF is the Fermi temperature and T-c( (0)) is the superconducting transition temperature obtained in the mean fie ld approximation. We also demonstrate that a weak 3D character of the super conducting fluctuation pushes T,up to be finite while the superconducting f luctuation is suppressed significantly at T < T-c. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.