The ABC of Aharonov Effects
The ABC of Aharonov Effects
复制标题
阿哈罗诺夫效应的基本知识
作者：
K. Richter
图 1：介观环导体的草图，基于层状半导体中的二维电子气，并耦合到两条引线。 Rashba 自旋轨道相互作用将电子自旋耦合到垂直于电子动量（红色）的有效径向磁场（蓝色）以及与两个半导体结构之间的界面相关的电场。对于有限自旋轨道耦合，电子自旋不能绝热地保持相对于该径向场的固定方向，而是围绕引导矢量进动，该引导矢量本身围绕张角为 θ 的圆锥形表面轨迹[参见方程（1）]。（真正的绝热性将对应于 θ= 90。）穿过电场的电子在其静止坐标系中会经历与电子磁矩相互作用的磁场。这种相互作用是自旋轨道耦合的基础，它导致原子中电子的能量根据其自旋状态分裂。在电子沿着两种不同半导体之间的界面传播的情况下，从一种导带能量到另一种导带能量的转变表现为局部电场，从而引起自旋轨道相互作用。此处，所产生的动量相关的自旋分裂被称为 Rashba 效应 [1]。由于效应的大小取决于结参数并且可以通过外部电场控制，因此 Rashba 相互作用为“自旋轨道电子学”提供了一种很有前途的工具，其中可以通过纯电气机制来操纵自旋。
Figure 1: Sketch of a mesoscopic ring conductor, based on a two-dimensional electron gas in a layered semiconductor, and coupled to two leads. Rashba spin-orbit interaction couples the electron spin to an effective radial magnetic field (blue) perpendicular to the electron momentum (red) and to the electric field associated with the interface between the two semiconductor structures. For finite spin-orbit coupling, the electron spin cannot adiabatically maintain a fixed orientation with respect to this radial field but precesses around a guiding vector that itself tracks around a conical surface with opening angle θ [see Eq.(1)].(True adiabaticity would correspond to θ= 90.)An electron traveling through an electric field experiences, in its rest frame, a magnetic field that interacts with the electron’s magnetic moment. This interaction is the basis of spin-orbit coupling, which causes a splitting of the energies of electrons in atoms depending on their spin state. In the case of electrons traveling along an interface between two different semiconductors, the transition from one conduction-band energy to another manifests itself as a local electric field that gives rise to a spin-orbit interaction. Here, the resulting momentum-dependent spin splitting is known as the Rashba effect [1]. Because the magnitude of the effect depends on the junction parameters and can be controlled by an external electric field, the Rashba interaction offers a promising tool for “spin-orbitronics,” in which spins can be manipulated through purely electrical mechanisms.