d-Wave Order Parameter in Bi2212 from a Phenomenological Model of High T$_c$ Cuprates

A phenomenological lattice model of high $T_c$ cuprates including order parameter phase fluctuations is considered within the BCS approximation, to interpret the experimental data from ARPES measurements on Bi2212 samples. A Kosterlitz-Thouless (KT) transition temperature $T_c^{KT}$ is estimated below the mean field transition $T_c^{MF}$, phase boundaries between competing order parameters of different symmetries are obtained and best model parameters, fitting the ARPES gap of $d_{x^2-y^2}$ symmetry, are determined. Variation of $T_c^{KT}$, as a function of the dopant concentration $\delta$, is in qualitative agreement with experiments.