双成分模型及YBCO/Pb结沿c轴的Josephson效应

根据巡游载流子与具有负U关联的近局域载流子相杂化的双成分模型研究了YBCO/Pb结沿c轴的Josephson效应．在此模型中巡游载流子具有s波对称性，能隙较小．近局域载流子具有d波超导电性，其临界温度决定体系的转变温度，沿c轴的Josephson电流I_c主要由s波贡献．由计算得到的s波能隙大小及其相应的临界温度较好地解释了实验观测到的零温隧穿电流与结电阻之积I_c（O）R_N以及I_c随温度的变化．此外，该模型还能解释在施加 关键词：

THE TWO-COMPONENT MODEL AND THE JOSEPHSON EFFECT ALONG c-AXIS ON YBCO/Pb JUNCTION

Using the two-component model with the mixing of itinerant carriers and nearly localized carriers with negative -U correlation we study the Josephson effect along c-axis on YBCO/Pb junction.In this model the itinerant carriers have s-wave symmetry and smaller energy gap.The nearly localized carriers have d-wave symmetry and its critical temperature establishes the superconducting transition temperature of the system.the Josephson current is contributed completely by the s-wave.Using the calculated s-wave energy gap and the corresponding critical temperature we have quantitatively explained the product of Josephson current at 0K and junction resistance, I_c(0)R_N ,and the variation of I_c with temperature.In addition,we can explain the observed variation of I_c with bias voltage and the Fraunhofer pattern,and the model is consistent with other SQUID experiments probing the symmetry of order parameter of YBCO.Therefore,the two-component model gives a consistent explanation for the two kinds of experimental results which seem to contradict with each other.We also briefly discuss the experimental method which can distinguish different models.