$P{b}_{0.4}B{i}_{1.6}S{r}_{2}C{a}_{1}C{u}_2{O}_{8+x}$ and Oxygen Stoichiometry: Structure, Resistivity, Fermi Surface Topology and Normal State Properties

Abstract

$P{b}_{0.4}B{i}_{1.6}S{r}_{2}CaC{u}_2{O}_{8+x}$ ($Bi(Pb)-$2212) single crystal samples were studied using transmission electron microscopy (TEM), $ab-$plane (${\rho }_{ab}$) and $c-$axis (${\rho }_c$) 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 $80-130$K. He-annealed samples exhibit a much higher $c-$axis resistivity and $d{\rho }_c/dT<0$ 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 $\bar{M}$ point and exhibits orthorhombic symmetry. There are flat, parallel sections of the FS, about 60\% of the maximum possible along $k_x=k_y$, and about 30\% along $k_x=-k_y$. The wavevectors connecting the flat sections are about $0.72(\pi ,\pi )$ along $k_x=k_y$, and about $0.80(\pi ,\pi )$ along $k_x=-k_y$, rather than $(\pi ,\pi )$. The symmetry of the near-Fermi-energy dispersing states in the normal state changes between oxygen-annealed and He-annealed samples.

APS_REVTEX 3.0, 49 pages, including 11 figures, available upon request. Submitted to Phys. Rev. B.