高Tc超导体Y-Ba-Cu-O超导临界涨落的正电子湮没研究  

A STUDY OF THESUPERCONDUCTIVITY GRITICAL FLUCTUATIONOF HIGH Tc SUPERCONDUCTOR Y-Ba-Cu-O BY POSITION ANNIHILATION

作　　者：陈岭[1] 滕敏康[1] 

机构地区：[1]南京大学物理系

出　　处：《南京大学学报（自然科学版）》1989年第1期36-40,共5页Journal of Nanjing University（Natural Science）

摘　　要：利用正电子湮没技术寿命谱测量系统首次细致地测量了高Tc超导体Y-Ba-Cu-O材料在Tc转变点附近的正电子湮没寿命谱参数的变化特性,发现在Tc处正电子湮没寿命呈峰。根据超导涨落的KSS理论和BCS超导理论的形式,推导出了正电子在超导转变溫度Tc附近超导态和正常态内的湮没率公式。经计算机数值积分得到与实验一致的结果,从而解释了实验上发现的异常现象。Position annihilation lifetine techniquo was used to study the new material, high Te superconductor Y-Ba-Cu-O, in the transition temperature region. For the first time, the anomaly of positron lifetime was discovered and the posi- tron mean lifetime showed a peak at Te point. For the sake of understanding this nnusual phenomenon, po itron annihilation rates in both high and low Tc snporconductors wore calculated by eonsidering the interaction between the thormalizod positrons and electrons in superconducting and normal state in the framework of BCS theory and KSS model. By properly choosing parameters (for instance E_F=0.7ev), the above-mentioned anomaly is predicated and in accordance with the experimental results. On the other hand, the theoretical calculation does agree with the Green Function procedure in the case of conventional low temperature superconductor when Fermi energy E_F is taken to be 5ev.

关 键 词：高TC超导体 正电子湮没 临界涨落 

分 类 号：O511.1[理学—低温物理]