The pseudogap and the superconducting order parameter in inhomogeneous Bi2Sr2CaCu2O8+δ

Recent experiments on Bi2Sr2CaCu2O8C8+delta (Bi2212) have provided compelling evidence that the samples are inhomogeneous on a nanoscale, with spatially separated superconducting gap (SG) and nonsuperconducting, pseudogap (PG) regions that arise from hole-hole and particle hole pairings, respectively. We compare and contrast the nonphase sensitive experiments that cannot distinguish these orderings from the phase-sensitive experiments that can. Although the wave vector dependence of the pseudogap is highly anisotropic, we conclude that in Bi2212, the c-axis quasiparticle tunneling is incoherent and that the c-axis supercurrent arises solely from a rather isotropic s-wave superconducting order parameter (OP) for T < T-c.