Variation ofTcand transport properties with carrier concentration in Y- and Pb-doped Bi-based superconductors

Electrical resistivity, magnetic susceptibility, and the Hall voltage of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{Ca}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Y}}_{\mathit{x}}$ ${\mathrm{Cu}}_2$ ${\mathrm{O}}_{8+\mathit{y}}$ (Bi 2:2:1:2) and (${\mathrm{Bi}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Pb}}_{\mathit{x}}$ ${)}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{Ca}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{10+\mathit{y}}$ (Bi 2:2:2:3) samples are measured as a function of temperature. A metal-insulator transition originating from the change of carrier concentration is found in the Bi 2:2:1:2 system at x≃0.55. Analysis of the electrical resistivity in the insulating region suggests that the transport is governed by a variable-range-hopping mechanism in the low-temperature region and phonon-assisted hopping of polarons in the high-temperature region. A universal dome-shaped ${\mathit{T}}_{\mathit{c}}$ versus ${\mathit{n}}_{\mathit{H}}$ variation is observed in the Bi 2:2:1:2 and Bi 2:2:2:3 systems, which is similar to that reported in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ and ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ systems. Various normal-state parameters, such as the effective mass of the carrier, Fermi energy, density of states at the Fermi level, and correlation energy, are calculated and compared to those reported in the literature.