The physics and technology of low-dimensional electronic systems at terahertz frequencies

在过去的20年里，对介观量子限制电子系统的研究揭示了丰富的令人兴奋的基础物理。这些研究没有显示出减弱的迹象，因为器件制造和测量技术的进步使人们能够进行更复杂的结构和更复杂的实验。在许多重要的介观器件中，如二维电子系统、层状半导体结构、半导体量子点和横向限制的线、点和其他几何结构，特征能量尺度对应于太赫兹（THz）频率范围（1 THz = 1x10^12 Hz = 4.1 meV），直到最近才很难获得。此外，虽然大多数介观系统的研究使用直流传输或光学（近红外）技术，宝贵的信息的状态和动态的载体在凝聚态系统中，不能通过直流传输方法，可以潜在地访问通过动态（高频）的电子响应。我们的愿景是通过开发和利用太赫兹频率技术，特别是导波技术，探索量子限制电子系统的太赫兹频率/皮秒响应，在介观电子系统的研究中创造一个台阶式的变化。我们将开发准光学技术，以产生（和检测）单周期太赫兹/皮秒电子脉冲相邻的介观系统在低温恒温器，避免RC带宽限制固有的问题，在以前的高频（高达千兆赫兹范围）的电气测量。我们还将开发方法来执行皮秒分辨率测量，能够监测单电子的空间位置比以前快三个数量级;这将为介观物理学领域提供通用技术，其中量子态的发生或变化发生在皮秒时间尺度上。该计划包括量子限制电子系统中太赫兹频率科学和技术的共生发展，将在国际上独一无二，并将为介观物理学开辟一个重要的新方向。

Over the last 20 years, the study of mesoscopic quantum-confined electronic systems has revealed a wealth of exciting and fundamental physics. These studies show no sign of abating as advances in device fabrication and measurement techniques enable ever more intricate structures and more sophisticated experiments to be made. The characteristic energy scale in many important mesoscopic devices such as two-dimensional electron systems, layered semiconductor structures, semiconductor quantum dots, and laterally-confined wires, dots, and other geometries, corresponds to the terahertz (THz) frequency range (1 THz = 1x10^12 Hz = 4.1 meV), which until recently has been difficult to access. Furthermore, although the majority of studies of mesoscopic systems use dc transport or optical (near-infrared) techniques, invaluable information on the states and dynamics of carriers in condensed matter systems, not obtainable by dc transport methods, can potentially be accessed though the dynamic (high frequency) electronic response. Our vision is to create a step-change in the study of mesoscopic electronic systems by developing and exploiting THz fre-quency technology, and in particular, guided-wave techniques, to probe the THz frequency / picosecond response of quantum-confined electronic systems. We will develop quasi-optical techniques to generate (and detect) single-cycle THz / picosecond electronic pulses adjacent to the mesoscopic system in the cryostat, avoiding the RC bandwidth-limiting problems inherent in previous high frequency (up to the gigahertz range) electrical measurements. We will also develop the methodology to perform picosecond-resolution measurements capable of monitoring the spatial position of single electrons three orders-of-magnitude faster than achieved previously; this will provide a generic technology for the field of mesoscopic physics where the onset of, or change in, a quantum state occurs on a picosecond time scale. This programme, which comprises the symbiotic development of THz frequency science and technology in quantum con-fined electronic systems, will be unique internationally and will open an important new direction for mesoscopic physics.