YBCO颗粒膜的非平衡微波响应与Kosterlitz-Thouless相变

NONEQUILIBRIUM MICROWAVE RESPONSE AND KOSTERLITZ THOULESS TRANSITION IN YBCO GRANULAR FILMS

报道了ＹＢａ２Ｃｕ３Ｏ７－δ（ＹＢＣＯ）颗粒膜的微波辐射（λ＝８ｍｍ）响应特征．实验结果表明：ＹＢＣＯ颗粒膜的微波响应行为不能用辐射热效应来描述，而应当属于非平衡响应行为．在超导转变温度Ｔｃｏ以下温区，非平衡微波响应信号电平随样品电阻Ｒ趋于零而消失，并且对弱的外磁场十分灵敏．在对样品的直流ＩＶ特性进行了仔细测量后发现，样品的电输运行为具有准二维结构特征，可以用ＫｏｓｔｅｒｌｉｔｚＴｈｏｕｌｅｓ（ＫＴ）相变模型加以描述．在此基础上，分析结果表明：ＹＢＣＯ颗粒膜中的非平衡微波响应机制可能与磁通“涡旋反涡旋”

Abstract The characteristic of microwave radiation ( λ =8mm) response of YBCO granular films was reported. Experimental results show that the response behavior can be described with nonequilibrium response effect, instead of thermal effect model. Near below the transition temperature T co , nonequilibrium microwave response signal decays gradually and disappears with the sample resistance becoming zero. It was also found that the response signal is very sensitive to a weak magnetic field. The sample I V curve was studied carefully, and the Kosterlitz Thouless transition model can be used to describe the two dimensional transport characteristic of the YBCO granular films. Based on the analysis and experimental results, we believe that the mechanism of nonequilibrium microwave response may be related with the breaking of the votex antivotex pair in high T c superconductor.