Electrical Resistivity Parallel to the c-axis of Bi1.74Pb0.38Sr1.88CuO6+δ
in Magnetic Fields

Two kinds of pseudogap temperatures T* and T** have been deduced from the out-of-plane resistivity of Bi1.74Pb0.38Sr1.88CuO6+δ in magnetic fields up to 27 T. The pseudogap formed at T* is independent of magnetic fields, while another pseudogap at T** is suppressed by the application of magnetic fields. Taking into account that the hole-concentration and magnetic-field dependences of T** resemble those of the superconducting transition temperature Tc, it has been concluded that the pseudogap temperature correlating to the superconductivity is not T* but T**. The gap at T* may relate to a different phenomenon with larger energy scale such as the antiferromagnetic interaction because of the universality with doping in different systems. In addition, T* exists even in the nonsuperconducting heavy overdoping region.
IMR, Tohoku University: K. Kudo, Y. Miyoshi, T. Sasaki, N. Kobayashi
Reference: K. Kudo, Y. Miyoshi, T. Sasaki and N. Kobayashi, "Pseudogap formation and the superconductivity in Bi1.74Pb0.38Sr1.88CuO6+δ studied by the out-of-plane resistivity in magnetic fields", cond-mat/0405106.
Bi1.74Pb0.38Sr1.88CuO6+δのc軸抵抗を最大27 Tの磁場中で測定し,2種類の擬ギャップ温度T*,T**を見出した.T*以下で開く擬ギャップは磁場に依存せず,一方,T**以下で開く擬ギャップは抑制される.T**とTcのホール濃度依存性と磁場依存性がよく似ていることから,T**は超伝導の前駆現象となる擬ギャップの開く温度であると結論した.一方,T*については,系に依存しないこと,非超伝導相にも存在することなどから,反強磁性相関のような他の励起に起因すると考えられる.
東北大学 金属材料研究所:工藤一貴,三好良幸,佐々木孝彦,小林典男