正常导体-超导体(n-s)多层薄膜系统的电子态

本文是文献1—3]工作的继续,在前面工作中发展的方法被推广到讨论半无限n-s多层膜结构的电子态,构造这种系统的步骤如下:首先把一完整无限的晶体沿两个分开的原子平面切割开得一晶体薄膜,它可以是正常金属也可以是超导体;然后把薄膜A和B通过金属型接触形成一混合单元O;最后沿垂直于界面方向依次排上单元O构成一半无限多层膜结构,我们导出了上述每一步所对应的单位子格林函数,对两种不同正常金属组成的多层膜结构,给出了单粒子状态密度和能带的数值计算结果,当两种正常金属相同时,所得的公式结果与文献7]等价,进而,对薄膜 关键词：

ELECTRON STATES OF A NORMAL-SUPERCONDUCTING MULTI-FILM STRUCTURE

This work is a continuation of the ref. 1, 2] and 3]. The method developed in the previous works is extended to the study of a semi-infinite n-s multi-film structure. This structure is constructed as follows. First, we obtain a crystal thin film which may be either normal or superconducting by cutting a perfect infinite crystal at two separate paralled atomic planes. And then a mixed unit O composed of a thin film A and a thin film B is formed by close metallic contact. Finally, a semi-infinite multi-film structure is constructed by placing unit O's consecutively along the direction perpendicular to the interface. The corresponding single particle Green's functions for each step have been calculated. When film A and B belong to different normal metal, the results of the numerical calculation for both the single particle density of state and the energy band of such a structure have been given. When films A and B are made of the same normal metal, the results are equivelent to that of ref 7]. Futher-more, the equations for the case that one of the thin films is superconducting have been derived. The numerical results show that 1) the whole n-s multi-film structure is superconducting, and a finite peak appears in single particle density of states near the original gap edge, 2) the whole structure is gapless just as expect.