Theoretical Study of Quantum Transport Phenomena through an Atom Sized Contact.

当扫描隧道显微镜的尖端与金属表面接触，然后缓慢抬起时，在尖端和表面之间形成原子大小的接触。这样就形成了一个原子大小的桥，它的横截面由几个原子到几十个原子组成。当端部抬起时，测量作为桥的拉伸长度的函数的桥的电导。实验上观察到电导的阶梯式变化，单位大约为2 e ^<>h。为了满足电子学中从介观尺度到原子尺度的缩小要求，有必要研究这种原子尺度系统中发生的各种现象。考虑到这一点，我们检查的原子大小的桥和电子之间的库仑相互作用的量子化电导通过一个原子大小的桥的收缩结构的影响。主要研究结果如下：1.收缩结构的影响 ...更多信息 原子大小的桥：电导的阶跃变化受到原子大小的桥的形状的破缺对称性的干扰.电子之间的格位内库仑相互作用的影响：在有限温度下，库仑相互作用引起各种类型的电子-电子散射过程，子带间和子带内散射过程，Umklapp和正常散射过程，强烈影响原子大小的桥的量子输运性质。因此，得出以下结论。(1)在电导平台处，电导值与2 e2/h的通用值的倍数的偏差随着温度的降低而增大。这种温度依赖性对于更强的库仑相互作用更强。(2)在台阶附近，出现了一个山谷结构，作为桥梁拉伸长度的函数。随着温度的降低，山谷变得越来越窄。当库仑相互作用变强时，谷的深度显著增加。少

When the tip of a scanning tunneling microscope is brought into contact with a metal surface and then lifted up slowly, an atom-sized contact is formed between the tip and the surface. An atom-sized bridge is thus formed and its cross section consists of a few atoms to a few tens of atoms. Conductance of the bridge is measured as a function of the stretching length of the bridge, while the tip is lifted up. A stepwise variation of the conductance is experimentally observed roughly in units of 2e^<>h. In order to satisfy requirements for downsizing from mesoscopic scale to atomic scale in electronics, it is necessary to examine various phenomena occurring in such atom-sized systems. With this in mind, we examine the effects of the constricted structure of the atom-sized bridge and the effects of the Coulomb interaction between electrons on the quantized conductance through an atom-sized bridge. The obtained results are summarized as follows.1. The effects of the constricted structure of … More the atom-sized bridge :Stepwise variation of the conductance is disturbed by the broken symmetry of the shape of the atom-sized bridge.2. The effects of the intra-site Coulomb interaction between electrons :At finite temperatures, the Coulomb interaction causes various types of electron-electron scattering processes, inter-subband as well as intra-subband scattering processes and Umklapp as well as normal scattering processes, and strongly affects the quantum transport property of an atom-sized bridge. As a result, the following are derived.(1) At the conductance plateau, the deviation of the conductance value from multiples of the universal value of 2e2/h grows as the temperature is decreased. This temperature dependence is stronger for stronger Coulomb interactions.(2) Near the step, a valley structure appears as a function of the stretching length of the bridge. As the temperature is decreased, the valley gets narrower. The depth of the valley grows significantly, as the Coulomb interaction becomes stronger. Less