STRONG-COUPLING FEATURES DUE TO QUASI-PARTICLE INTERACTIONS IN 2-DIMENSIONAL SUPERCONDUCTORS

I calculate the effect of interactions among superconducting quasipart icles in two-dimensional (2D) a superconductor at T = 0. The strength of the effective interaction among the quasiparticles is essentially g iven by the screened Coulomb interaction which has strength at low fre quency because of the gapless nature of the plasmon. This is in contra st to three dimensions where the effective interaction has negligible weight at frequencies similar to Delta, the superconducting gap. The q uasiparticle interactions give rise to strong-coupling effects in expe rimental quantities which are beyond the conventional Eliashberg treat ment of superconductivity. The present calculation offers an explanati on of why these effects are much larger in 2D than in 3D superconducto rs and, in particular, why the analogous strong-coupling effects due t o quasiparticle interactions are seen in data on the quasi-2D cuprate superconductors. The strong-coupling features seen in data on the cupr ates are discussed in light of the present calculation. (C) 1998 Elsev ier Science B.V. All rights reserved.