Two Kinds of Pseudogaps in Bi_<1.79> Pb_<0.37 >Sr_<1.86>CuO_<6+δ> Studied by the Out-of-Plane Resistivity in Magnetic Fields(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We report the out-of-plane resistivity of Bi_<1.79>Pb_<0.37>Sr_<1.86>CuO_<6+δ> single crystals with various doping levels in magnetic fields up to 15T parallel to the c-axis. By using the low-T_c system sensitive to magnetic fields, two kinds of pseudogaps PG1 and PG2 are found at T_1 and T_2 below which the nonmetallic resistivity starts to develop and to be suppressed in magnetic fields with decreasing temperature, respectively. The doping dependence of T_2 exhibits a dome-like shape similar to T_c, indicating the close relation between PG2 and the superconductivity, while T_1 decreases monotonically with increasing the doping level. Systematic hole-doping reveals that T_1 exists even in the heavily overdoped nonsuperconducting sample, indicating the weak relation between PG1 and the superconductivity.
社団法人日本物理学会の論文
2006-12-15