Acquisition of a High Frequency Measurement System for Mesoscopic Samples

获得用于介观样品的高频测量系统

• 批准号: 9625550
• 负责人: Richard Webb
• 金额: $ 23.23万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-07-01 至 1997-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9625550&HistoricalAwards=false
• 关键词: Acquisition; Frequency; Measurement; System; Mesoscopic

9625550 Webb The goal of this project is to elucidate the high frequency properties of mesoscopic structures using a state-of-the-art high frequency low noise measurement system. During the last decade it was discovered that a wave mechanics approach must be adopted when describing the propagation of an electron through any small conductor, including insulators and dirty metals as well as nearly perfect crystals. Electron interference effects, which are responsible for many of the large fluctuations observed in transport experiments, can be traced to the existence of large phase coherence times for the wave function of the electron. These large times in turn have lead to the discovery of persistent currents in normal metals, Universal Conductance Fluctuations (UCF), h/e & h2e Aharonov-Bohm effects, non-local quantum effects, length-independent conductance fluctuations, and an understanding of how these new quantum effects ensemble average to their classical values. Very little is known about the properties of the wavefunction which describes systems on time scales comparable to the coherence time (t~10-9 sec). The recent discovery that it is possible to make two terminal mesoscopic devices through which we can control the passage of electrons, one at a time, by using a third capacitively coupled gate electrode to the sample has generated much hope that these devices might be the transistors of the future. The frequency at which these single electrons pass through the device is f=IDc/e and is on the order of lx109 Hz for most samples studied to date. The applications of such a technology are quite extensive. They range from transistors to ultra-sensitive electrometers and current standards. In this project we will systematically explore the high frequency properties of these types of mesoscopic systems by using a new instrument that will allow us to directly measure the high frequency transport and magnetic properties of our samples. We believe that attemp ts to probe mesoscopic systems on a time scale comparable to the coherence time of the wavefunction will almost certainly produce a better understanding of the true nature of the quantum physics of these systems. %%% Since the physics of small structures provides the foundation upon which future electronic industry technologies may be based, it is extremely important that we identify and understand all the potentially relevant physical properties that these systems exhibit. Only after these properties are reasonably well understood can we attempt to propose to use any one of them in a new or improved technology. The work described here is a relatively new direction for the studies of mesoscopic structures: we believe experiments in the area of magnetic and transport properties of mesoscopic structures are likely to discover new phenomena which have yet to be anticipated and expand our fundamental knowledge of condensed matter science. ***

这个项目的目标是利用最先进的高频低噪声测量系统来阐明介观结构的高频特性。在过去的十年中，人们发现，当描述电子通过任何小导体的传播时，必须采用波动力学的方法，包括绝缘体和脏金属以及近乎完美的晶体。电子干涉效应是导致输运实验中观察到的许多大波动的原因，它可以追溯到电子波函数的大相位相干时间的存在。这些大时间反过来又导致了正常金属中持续电流的发现，通用电导波动（UCF）， h/e &； h Aharonov-Bohm效应，非局部量子效应，长度无关的电导波动，以及对这些新量子效应如何平均到它们的经典值的理解。在相干时间（t~10-9秒）的时间尺度上，描述系统的波函数的性质所知甚少。最近的发现是有可能制造两个终端介观器件，通过它们我们可以控制电子的通过，一次一个，通过使用第三个电容耦合栅极到样品，产生了很大的希望，这些器件可能是未来的晶体管。这些单电子通过装置的频率为f=IDc/e，迄今为止研究的大多数样品的频率为lx109 Hz。这种技术的应用是相当广泛的。它们的范围从晶体管到超灵敏静电计和电流标准。在这个项目中，我们将通过使用一种新的仪器系统地探索这些类型的介观系统的高频特性，这将使我们能够直接测量样品的高频输运和磁性。我们相信，尝试在与波函数相干时间相当的时间尺度上探测介观系统，几乎肯定会更好地理解这些系统的量子物理的真实本质。由于小型结构的物理学为未来的电子工业技术提供了基础，因此我们识别和理解这些系统所表现出的所有潜在的相关物理特性是极其重要的。只有在对这些特性有了相当充分的了解之后，我们才能尝试在新的或改进的技术中使用它们中的任何一个。本文所描述的工作是介观结构研究的一个相对新的方向：我们相信在介观结构的磁性和输运性质领域的实验可能会发现尚未预料到的新现象，并扩展我们对凝聚态科学的基础知识。＊＊＊