講演題目：　Tunneling Measurements on Intrinsic Josephson Junctions of
                   Bi2Sr2CaCu2O8+x Single Crystals

講　師　：　Prof. Hu-Jong Lee
　　　　　(Pohang University, Korea)

日　時　：　平成12年8月25日 16:00〜
場　所　：　北海道大学理学部２号館大学院講義室（2-2-11）

要　旨　：
In highly anisotropic layered cuprate superconductors such as Bi2Sr2CaCu2O8+x material Josephson coupling is established between neighboring CuO2 double layers at temperatures below the superconducting transition of the layers. Thus, in a piece of cuprate single crystal these intrinsic Josephson junctions (IJJs) are stacked in series. Studies on the IJJs provide valuable information on important properties of the high-Tc materials, in both the superconducting and the normal states. In this presentation I will focus especially on the surface Josephson junction, which consists of surface CuO2 layer and the adjacent inner CuO2 layer, in a small mesa formed on a crystal. The surface layer, which is in direct contact with a thick normal-metallic (Au) electrode, exhibits depressed superconductivity due to the proximity effect but not by any surface degradation effect. Then, I will present the zero-crossing Shapiro steps observed in the surface junction under radio-frequency (rf) irradiation (of several tens of GHz range). Only the surface junction with weakened Josepshon coupling exhibits stable zero-crossing current steps. Finally, I will present the rf response of HgI2-intercalated Bi2Sr2CaCu2O8+x single crystals with weakened Josephson coupling in all the intrinsic junctions rather than just the surface one, where rf-induced fluxon motion was observed instead of the zero-crossing steps.

小田 研　（北海道大学大学院理学研究科）
(011-706-3575、moda@sci.hokudai.ac.jp)
 北海道大学・大学院理学研究科・物理学専攻