高温铜氧化物超导体的正常态——赝隙金属态

对高温铜氧化物超导体的正常态,首先回顾了有关其性质的9点重要实验结果.在此基础上,论证双子系统、二维Hamilton量是描写HTS正常态的适宜的出发点.以此Hamilton量采用Kaga退耦合近似的Green函数法经数值计算,得到了随温度而变的态密度中赝隙,与角分辨光电发射实验结果定性一致.理论还表明此Hamilton量具有以d波为主的d+s对称性的超导序参量,这和实验相符.进一步指出,高温铜氧化超导体中的量子电子液体是近Fermi液体,其中退局域化态与近局域化态共存,而近局域载流子在任一有限温度下有一定几率形成近局域载流子对.     

掺杂的高温超导体的自旋晶格弛豫率

本在赝隙和剩余态密度基础上对ＹＢａ２（Ｃｕ１－ｘＺｎｘ）３Ｏ７及Ｔｌ２Ｂａ２ＣｕＯ６＋ｙ（Ｔｃ＝４０Ｋ）在超导态下的自旋晶格弛豫行为进行了研究，在低于Ｔｃ的整个温区内计算值与实验符合较好。研究表明在稍低于Ｔｃ的温区赝隙导致了ＢＣＳ理论预言的相干峰消失，而在低温，剩 余态密度对体系的自旋晶格弛豫率的贡献起了主要作用。     

EFFECT OF THE SUBSTITUTION OF Ga AND Sn FOR Cu ON THE ELECTRONIC STRUCTURE AND SUPERCONDUCTIVITY OF La1.85Sr0.15CuO4

The electronic structure of La_1.85Sr_0.15CuO₄， as well as the two cases of substitution of Ga and Sn for Cu, has been studied by the recursion method. The change of hole concentration and the effective local magnetic moment have also been calculated. Our calculations show that Ga and Sn destroy the two-dimensional character of the CuO₂ plane and lead to the disorder of the electronic structure, accompanied by the migration of electrons which canines the decrease of the hole concentration in the CuO₂ planes. From our point of view, these changes may be responsible for the destruction of superconductivity of the Ga and Sn-doped systems.     

s+d混合波对称性下计入库仑作用和Van Hove奇异性的超导转变温度和同位素效应

本文在ｓ＋ｄ混合波对称性下研究了ＶａｎＨｏｖｅ奇异性、准粒子配对相互作用各向异性并再计入库仑排斥势对超导转变温度（Ｔｃ）和同位素效应的联合效应．结果表明，ＶａｎＨｏｖｅ奇异性和各向异性都能显著地增高Ｔｃ，库仑作用则降低Ｔｃ．库仑作用和ＶａｎＨｏｖｅ奇异性都能减小同位素效应指数（α），各向异性和ｄ波成分则增大α．计入库仑作用后α就随ＣｕＯ２面内各向异性参量增大而增大．由此可以推测，如果实验上肯定了高温超导体的序参量是以ｄ波为主，则高温超导电性为非声子机制的可能性就比较大．此结论与根据有关文献作出的判断相符．     

EFFECT OF THE SUBSTITUTION OF Ga AND Sn FOR Cu ON THE ELECTRONIC STRUCTURE AND SUPERCONDUCTIVITY OF La1.85Sr0.15CuO4

The electronic structure of La_1.85Sr_0.15CuO₄, as well as the two cases of substitution of Ga and Sn for Cu, has been studied by the recursion method. The change of hole concentration and the effective local magnetic moment have also been calculated. Our calculations show that Ga and Sn destroy the two-dimensional character of the CuO₂ plane and lead to the disorder of the electronic structure, accompanied by the migration of electrons which canines the decrease of the hole concentration in the CuO₂ planes. From our point of view, these changes may be responsible for the destruction of superconductivity of the Ga and Sn-doped systems.     

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：     

高温铜氧化物超导体的正常态--赝隙金属态

对高温铜氧化物超导体的正常态,首先回顾了有关其性质的9点重要实验结果.在此基础上,论证双子系统、二维Hamilton量是描写HTS正常态的适宜的出发点.以此Hamilton量采用Kaga退耦合近似的Green函数法经数值计算,得到了随温度而变的态密度中赝隙,与角分辨光电发射实验结果定性一致.理论还表明此Hamilton量具有以d波为主的d+s对称性的超导序参量,这和实验相符.进一步指出,高温铜氧化超导体中的量子电子液体是近Fermi液体,其中退局域化态与近局域化态共存,而近局域载流子在任一有限温度下有一定几率形成近局域载流子对.