Understanding nanoscale conductors

S. Datta
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引用次数: 1

Abstract

Summary form only given. It is common to differentiate between two ways of building a nanodevice: a top-down approach where we start from something big and chisel out what we want and a bottom-up approach where we start from something small like atoms or molecules and assemble what we want. When it comes to describing electrical resistance, the standard approach could be called a "top-down" one where we start from large complex resistors and work our way down to molecules primarily because our understanding has evolved in this top-down fashion. However, it is instructive to take a bottom-up view of the subject starting from the conductance of something really small, like a molecule, and then discussing the issues that arise as we move to bigger conductors. This is the subject of this tutorial lecture (S. Datta, Nanotechnology, vol. 15, p. S433, 2004). Remarkably enough, no serious quantum mechanics is needed to understand electrical conduction through something really small, except for unusual things like the Kondo effect that are seen only for a special range of parameters. The presentation begins with (1) energy level diagrams, (2) shows that the broadening that accompanies coupling limits the conductance to a maximum of (q¿2/h) per level, (3) describes how a change in the shape of the self-consistent potential profile can turn a symmetric current-voltage characteristic into a rectifying one, (4) shows that many interesting effects in "nanoelectronics" can be understood in terms of a simple model, and (5) introduces the nonequilibrium Green's function (NEGF) formalism as a sophisticated version of this simple model with ordinary numbers replaced by appropriate matrices. Finally the distinction between the self-consistent field regime and the Coulomb blockade regime and the issues involved in modeling each of these regimes are described.
了解纳米级导体
只提供摘要形式。构建纳米器件的两种方法通常是不同的:一种是自上而下的方法,我们从大的东西开始,凿出我们想要的东西;另一种是自下而上的方法,我们从原子或分子这样的小的东西开始,组装我们想要的东西。当涉及到描述电阻时,标准的方法可以被称为“自上而下”的方法,我们从大型复杂的电阻开始,一直到分子,主要是因为我们的理解是在这种自上而下的方式中发展起来的。然而,从一个非常小的东西的电导率开始,比如一个分子,然后讨论当我们移动到更大的导体时出现的问题,这是有益的。这是本教程的主题(S. Datta, Nanotechnology, vol. 15, p. S433, 2004)。值得注意的是,不需要严肃的量子力学来理解通过非常小的物体的导电,除了像近藤效应这样的不寻常的东西,它只能在特殊的参数范围内看到。演示从(1)能级图开始,(2)表明,伴随着耦合的展宽将电导限制在每级(q¿2/h)的最大值,(3)描述了自一致电位分布形状的变化如何将对称的电流-电压特性转变为整流特性,(4)表明“纳米电子学”中的许多有趣的效应可以用一个简单的模型来理解。(5)引入非平衡格林函数(NEGF)形式主义作为这个简单模型的复杂版本,用适当的矩阵代替普通数字。最后介绍了自洽场和库仑封锁场的区别,以及对这两种情况进行建模所涉及的问题。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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