BEC MODEL OF HIGH-T_cSUPERCONDUCTIVITY IN LAYERED CUPRATES

High-T c superconductivity in layered cuprates is described in a BCS-BEC formalism with linearly-dispersive s- and d-wave Cooper pairs moving in quasi-2D finite-width layers around the CuO 2 planes. This yields a closed formula for T c involving the layer width, the Debye frequency, the pairing energy and the in-plane penetration depth. The new formula has no free parameters and reasonably reproduces empirical values of superconducting T c s for 11 different layered superconductors over a wide doping regime including YBCO itself as well as other compounds like LSCO, BSCCO and TBCCO. In agreement with the London formalism, the formula also yields a fair description of the T c dependence of the lower critical magnetic field in highly underdoped YBCO.