Efficiency of electrical manipulation in two-dimensional topological insulators

We investigate the efficiency of electrical manipulation in a two-dimensional topological insulator by inspecting the electronic states of a lateral electrical potential superlattice in the system. The spatial distribution of the electron density in the system can be tuned by changing the strength of the externally applied lateral electrical superlattice potential. This provides us the information about how efficiently one can manipulate the electron motion inside a two-dimensional topo- logical insulator. Such information is important in designing electronic devices, e.g., an electric field effect transistor made of the topological insulator. The electronic states under various conditions are examined carefully. It is found that the dispersion of the mini-band and the electron distribution in the potential well region both display an oscillatory behavior as the potential strength of the lateral superlattice increases. The probability of finding an electron in the potential well region can be larger or smaller than the average as the potential strength varies. These features can be attributed to the coupled multiple-band nature of the topological insulator. In addition, it is also found that these behaviors are not sensitive to the gap parameter of the two-dimensional topological insulator model. Our study suggests that the electron density manipulation via electrical gating in a two-dimensional topological insulator is less effective and more delicate than that in a traditional single-band semiconductor.     

一种根据布朗运动测量玻尔兹曼常量的新方法

利用显微镜和CCD图像采集工具对聚丙烯小球的布朗运动进行了研究,通过拍摄粒子运动图像并利用MATLAB程序进行图片处理,读取每一时刻布朗粒子的坐标.基于对大量数据的统计分析,计算出了玻尔兹曼常量,与理论值的相对误差约为4%.同时,验证了布朗运动位移服从正态分布以及粒子位移均方值与时间成正比的关系.