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  

THE SUPERCONDUCTING TRANSITION TEMPERATURE AND ISOTOPE EFFECT UNDER S+D MIXED WAVE SYMMETRY INCLUDING COULOMB REPULSION AND VAN HOVE SINGULARITY

作　　者：孙久勋[1,2,3] 章立源[1,2,3] 冯小兵 

机构地区：[1]电子科技大学应用物理系 [2]北京大学物理系 [3]大连铁道学院基础部

出　　处：《低温物理学报》1997年第3期166-174,共9页Low Temperature Physical Letters

基　　金：国家自然科学基金;北京大学计算中心资助

摘　　要：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．Under the symmetry of the s+d mixed waves, the influences of three factors on superconducting transition temperature and isotope effect are investigated. The first factor is the Van Hove singularity, the second is the anisotropy of the pairing interaction between electrons,and the third is the Coulomb repulsion. The theoritical results show that both the Van Hove singularity and the anisotropy of pairing interaction are important factors to enhance T c , yet the Coulomb repulsion will decrease T c . We have also shown that both the Coulomb repulsion and the Van Hove singulavity can decrease the isotope effect exponent( α ), while the anisotropy and the d wave component will increase it. Taking into account the Coulomb repulsion, we have found that the value of α will increase as the anisotropic parameter in the CuO 2 plane increase. As experiments verify the order parameter of high T c superconductors is d wave dominant, one can postulate from this that maybe the high T c superconductivity is nonphononic mechanism. The conclusion is in accordance with the judgement derived from relevant literature.

关 键 词：高TC 超导转变温度 s+d混合波 同位素效应 

分 类 号：O511.1[理学—低温物理]