Crystal growth and anisotropic transport properties of high-Tc superconductors Bi2Sr2Can-1CunO2n+4+d (n = 2, 3)

Large high-quality single crystals of Bi2Sr2Can-1CunO2n+4+d (n = 2, 3) were successfully grown using an improved traveling solvent floating zone (TSFZ) method, which features a slow growth rate and steep temperature gradient along the melting zone. By measuring anisotropic resistivities and susceptibilities of Bi2Sr2CaCu2O8+d, the characteristic pseudogap temperature T* was studied as a function of doping. The T* suggest that the pseudogap is not simply a precursor of high-Tc superconductivity, but that the pseudogap and the superconducting gap compete with each other. The anisotropic resistivities of Bi2Sr2Ca2Cu3O10+d were also measured, revealing that the Tc remains fixed in the overdoped region while anisotropy decreases continuously. This anomalous behavior will be discussed in terms of the inequivalent hole doping, which occurs between two inequivalent CuO2 planes in the triple-layer system.