Critical temperature in layered superconductors

We consider Bose-Einstein condensation of preexisting Cooper pairs which are confined within quasi-2D laminar structure. We show that the spectral dimensionality ɑ of such systems should be described within fractional-dimensional scheme. From detailed calculations results that for ɑ > 3 results that one would expect enhancement of critical temperature up to the limit set by the Cooper pair binding energy. We show that in the laterally modulated systems there can arise ɑ > 3 case while for the optimally doped YBCO system there is experimental evidence that ɑ =4.