双成分模型及YBCO/Pb结沿c轴的Josephson效应  

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

作　　者：冯小兵[1] 章立源[1] 孙久勋[1] 

机构地区：[1]北京大学物理系

出　　处：《物理学报》1997年第3期596-603,共8页Acta Physica Sinica

基　　金：高等学校博士学科点专项科研基金和国家自然科学基金资助的课题

摘　　要：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Ｉｃ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Ｉｃ（０）ＲＮ以及Ｉｃ随温度的变化．此外，该模型还能解释在施加磁场时观测到的Ｆｒａｕｎｈｏｆｅｒ花样及Ｉｃ随偏压的变化，而且该模型与其他测量ＹＢＣＯ序参量对称性的各种ＳＱＵＩＤ实验相一致。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.

关 键 词：YBCO 巡游载流子 超导物理 约瑟夫森效应 

分 类 号：O511.1[理学—低温物理]