Fundamental Experimental Properties of Mesoscopic Systems

本文主要研究介观器件的量子力学相相干性。在低温下，大多数介观电路只表现出0.05到10ns之间的相干时间，人们相信，制造功能量子器件需要更长的时间。本研究将在比相相干时间短得多和比相相干时间长得多的时间尺度上系统地探索介观系统的相相干输运和磁性。将研究0至26 GHz测量电流对金属（含或不含磁性杂质）和半导体退相干的影响。利用基于SQUID的噪声温度计技术测量各种介观样品中的热力学电子温度，以验证最近的理论预测，即热力学可能在小型设备中崩溃。所有这些工作的目标是了解高频、材料和几何特性如何影响小系统的量子相干特性。参与本课程的研究生将学习如何使用现代制造技术制造各种量子器件，使用最先进的技术测量这些器件，并将理解广泛的固态理论。所有这些技能都是在工业、政府或大学生涯中取得成功所必需的。当元件的尺寸减小到几微米以下时，所有电路的低温性能都会发生显著变化。电子干扰和电荷量子化等量子效应是在这些设备中观察到的许多大电导波动的原因，并点燃了人们的希望，即可以建立一种革命性的新型快速相干量子设备，以帮助推动微电子工业的持续进步。许多提出的新器件需要很长的电子相干时间来最大化信号，然而大多数纳米级电路只表现出0.05到10纳秒之间的相干时间。本研究的重点是了解控制小型电路相相干时间的基本物理原理，并期望我们能够发现增加相相干时间的方法。我们将系统地探索小量子系统在比相相干时间更短和更长的时间尺度上的相相干输运特性，试图了解我们是否可以在不引起退相干的情况下操纵量子态。参与该项目的研究生将接受必要的培训，成为下一代微电子科学家。他们将学习如何使用现代制造技术制造各种量子设备，并使用最先进的技术测量这些设备。所有这些技能都是在工业、政府或大学生涯中取得成功所必需的。

This research is focused on investigations of the quantum mechanical phase coherence properties of mesoscopic devices. At low temperatures, most mesoscopic circuits only exhibit coherence times between 0.05 to 10 ns and it is believed that much longer times will be required to make functional quantum devices. This work will systematically explore the phase coherent transport and magnetic properties of mesoscopic systems on time scales much shorter and much longer than the phase coherence time. Studies of the effect of 0 to 26 GHz measurement currents on decoherence in metals (with and without magnetic impurities) and semiconductors will be made. Measurements of the thermodynamic electron temperature in a variety of mesoscopic samples will be made using SQUID based noise thermometer techniques in order to check the recent theoretical prediction that thermodynamics may break down in small devices. The goal of all this work is to understand how the high frequency, material, and geometrical properties effect the quantum coherence properties of small systems. The graduate students involved with this program will learn how to fabricate a variety of quantum devices using modern fabrication techniques, measure these devices using state-of-the-art techniques, and will comprehend a wide body of solid state theory. All these skills are necessary in order to become successful in an industrial, government, or university career.%%%The low temperature properties of all electrical circuits can be significantly changed when the dimensions of the elements are reduced below a few microns. Quantum effects such as electron interference and charge quantization are responsible for many of the large conductance fluctuations observed in these devices and have kindled hope that a revolutionary new class of fast coherent quantum devices can be built to help fuel the continuing progress in the microelectronics industry. Many of the proposed new devices require long electron coherence times in order to maximize the signal, yet most nano-scale circuits only exhibit coherence times between 0.05 to 10 nanoseconds. This proposed research is focused on understanding the underlying physics that controls the phase coherence time in small electrical circuits with the expectation that we will be able to discover ways to increase this time. We will systematically explore the phase coherent transport properties of small quantum systems on time scales much shorter and much longer than the phase coherence time in an attempt to understand if we can manipulate the quantum state without causing decoherence. The graduate students involved with this program will receive the training necessary to become a future generation of microelectronic scientists. They will learn how to fabricate a variety of quantum devices using modern fabrication techniques and measure these devices using state-of-the-art techniques. All these skills are necessary in order to become successful in an industrial, government, or university career.