Acquisition of a High Frequency Measurement System for Mesoscopic Samples

9625550 Webb该项目的目标是阐明介观结构的高频特性，使用最先进的高频低噪声测量系统。 在过去的十年中，人们发现，在描述电子通过任何小导体（包括绝缘体和脏金属以及几乎完美的晶体）的传播时，必须采用波动力学方法。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，可以追溯到电子波函数的大相位相干时间的存在。这些大的时间反过来又导致了正常金属中持续电流的发现，普适电导波动（UCF），h/eh& 2 e Aharonov-Bohm效应，非局域量子效应，长度无关的电导波动，以及这些新的量子效应系综如何平均到它们的经典值的理解。 很少有人知道的性质的波函数描述系统的时间尺度可比的相干时间（t~10-9秒）。 最近的发现是，有可能使两个终端介观器件，通过它，我们可以控制电子的通道，一次一个，通过使用第三个电容耦合栅电极的样品产生了很大的希望，这些设备可能是未来的晶体管。 这些单电子通过器件的频率为f=IDc/e，并且对于迄今为止研究的大多数样品而言，其为1 × 109 Hz的量级。 这种技术的应用非常广泛。 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，我们将系统地探索这些类型的介观系统的高频特性，通过使用一种新的仪器，这将使我们能够直接测量我们的样品的高频传输和磁性。 我们相信，在与波函数的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性质。 %%% 由于小结构的物理学提供了未来电子工业技术的基础，因此我们识别和理解这些系统所表现出的所有潜在相关物理特性是非常重要的。 只有在对这些性质有了相当充分的了解之后，我们才能试图提出在新的或改进的技术中使用它们中的任何一种。 本文所描述的工作是介观结构研究的一个相对较新的方向：我们相信，在介观结构的磁性和输运性质方面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。 ***

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. ***