Pb0.4Bi1.6Sr2CaCu2O8+x and oxygen stoichiometry: Structure, resistivity, Fermi-surface topology, and normal-state properties.

Pb0.4Bi1.6Sr2CaCu2O8+x (Bi(Pb)−2212) single crystal samples were studied using transmission electron microscopy (TEM), ab−plane (ρab) and c−axis (ρc) resistivity, and high resolution angle-resolved ultraviolet photoemission spectroscopy (ARUPS). TEM reveals that the modulation in the b−axis for Pb(0.4)−doped Bi(Pb)−2212 is dominantly of Pb−type that is not sensitive to the oxygen content of the system, and the system clearly shows a structure of orthorhombic symmetry. Oxygen annealed samples exhibit a much lower c−axis resistivity and a resistivity minimum at 80− 130K. He-annealed samples exhibit a much higher c−axis resistivity and dρc/dT < 0 behavior below 300K. The Fermi surface (FS) of oxygen annealed Bi(Pb)−2212 mapped out by ARUPS has a pocket in the FS around the M̄ point and exhibits orthorhombic symmetry. There are flat, parallel sections of the FS, about 60% of the maximum possible along kx = ky, and about 30% along kx = −ky. The