杂质对两能带超导体性质的影响

本文中用一个简单的两能带模型讨论了费米面复连通性对超导体性质的影响。计算表明,它的效应与各向异性类似。利用Абрикосов和Горъков所发展的格林函数方法讨论了杂质散射的影响。有杂质时只有一个能隙,且大于纯超导体两个能隙中较小的一个。加杂后转变温度,临界磁场及其在T=0°K附近的温度系数下降,但转变点比热跳跃的相对值增加。低掺杂时在实验中同时测量这些量的变化可以定量地检验理论计算。高掺杂两能带超导体的性质与单能带情形完全相同。此外,利用本文的结果讨论了Pb膜的隧道效应实验和In-Sn,In-Pb系统中的转变温度反常。

THE INFLUENCE OF THE IMPURITY SCATTERING ON THE PROPERTIES OF TWO-BAND SUPERCONDUCTORS

A simple two-band model was used to investigate the influence of the multiconnec-tivity of the Fermi surface on the properties of superconductors. It was shown that the effect is analogous to that of anisotropy. The effect of impurity scattering was considered by the Green's function method of Абрикосов and Горъков. There is a unique energy gap for both bands in the presence of impurities. The new gap parameter is larger than the smaller one of the two gaps in the pure case. The critical temperature T_c, critical magnetic field H_c, and its temperature coefficient x near T=0°K are lowered with doping, while the jump in specific heat at the transition point is raised. The combined measurement of the relative changes of these quantities should provide a direct verification of the theoretical calculations. The properties of heavily doped two-band superconductors are identical with those in the single band case. Furthermore, the results obtained were used to discuss the tunnelling experiment on Pb films and the anomaly of critical temperature in the alloy systems of In-Sn and In-Pb.