Interface roughness, valley-orbit coupling, and valley manipulation in quantum dots
Interface roughness, valley-orbit coupling, and valley manipulation in quantum dots
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DOI：
10.1103/physrevb.82.205315
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发表时间：
2010-11-11
影响因子：
3.7
通讯作者：
Das Sarma, S.
中科院分区：
文献类型：
--
作者：
Culcer, Dimitrie;Hu, Xuedong;Das Sarma, S.
本文系统地研究了量子点的界面粗糙度及其对相干动力学过程的影响。由于一个尖锐的、平坦的界面而产生的势提升了最低能量谷的简并并产生了一组谷本征态。界面粗糙度的特征是界面位置的波动和势阶的大小。界面位置的变化，预计会发生在晶格常数的长度尺度上，降低了谷-轨道耦合的大小。在涉及两个（或多个）点的动力学中，界面电位阶跃的变化改变了谷-轨道耦合的大小，并诱导了不同谷特征态之间的跃迁。这种跃迁可以通过操纵两个点之间的偏置来实验研究，也可以通过电荷传感来检测。然而，如果表征界面位置的随机变量在量子点的顺序上随距离相关，这是不太可能但可能的，则相邻点的谷轨道耦合相位可能不同。在这种情况下，相似和相反的谷特征态之间的隧穿实际上是一个随机变量，不能被控制。我们提出了一种共振隧穿实验，可以识别在相似和相反谷本征态之间隧穿的矩阵元素。
We present a systematic study of interface roughness and its effect on coherent dynamical processes in quantum dots. The potential due to a sharp, flat interface lifts the degeneracy of the lowest energy valleys and yields a set of valley eigenstates. Interface roughness is characterized by fluctuations in the location of the interface and in the magnitude of the potential step. Variations in the position of the interface, which are expected to occur on the length scale of the lattice constant, reduce the magnitude of the valley-orbit coupling. Variations in the size of the interface potential step alter the magnitude of the valley-orbit coupling and induce transitions between different valley eigenstates in dynamics involving two (or more) dots. Such transitions can be studied experimentally by manipulating the bias between two dots and can be detected by charge sensing. However, if the random variable characterizing the position of the interface is correlated over distances on the order of a quantum dot, which is unlikely but possible, the phase of the valley-orbit coupling may be different in adjacent dots. In this case tunneling between like and opposite valley eigenstates is in effect a random variable and cannot be controlled. We suggest a resonant tunneling experiment that can identify the matrix elements for tunneling between like and opposite valley eigenstates.