Coherent Quasiparticle Weight and Its Connection to High-T_c Superconductivity from Angle-Resolved Photoemission

We study the doping and temperature dependence of the single-particle coherent weight, z A, for high-T_c superconductors Bi₂Sr₂CaCu₂O_8+x using angle-resolved photoemission. We find that at low temperatures the coherent weightz_A at (π, 0) is proportional to the carrier concentration x and that the temperature dependence of z_A is similar to that of the c-axis superfluid density. We show that, for a wide range of carrier concentration, the superconducting transition temperature scales with the product of the low-temperature coherent weight and the maximum superconducting gap.