BSCCO superconductors: Hole-like Fermi surface and doping dependence of the gap function

We use the gradient of the energy-integrated angle resolved photoemission. (ARPES) intensity in order to define precisely the Fermi surface (FS) in BS CCO superconductors. We show that, independent of the photon energy, the FS is a hole barrel centered at (pi, pi). Then, the superconducting gap along the FS is precisely determined from ARPES measurements on overdoped and un derdoped samples of Bi2212. As the doping decreases, the maximum gap increa ses, but the slope of the gap near the nodes decreases. Though consistent w ith d-wave symmetry, the gap with underdoping cannot be fit by the simple c os(k(x)) - cos(k(y)) form. A comparison of our ARPES results with available penetration depth data indicates that the renormalization of the linear T suppression of the superfluid density at low temperatures due to quasiparti cle excitations around the d-wave nodes is large and doping dependent.