Fundamental Experimental Properties of Mesoscopic Systems

本论文主要研究介观器件的量子力学相位相干特性。 在低温下，大多数介观电路仅表现出0.05至10 ns之间的相干时间，并且据信将需要更长的时间来制造功能性量子器件。 本文将在比相位相干时间短得多和长得多的时间尺度上系统地研究介观系统的相位相干输运和磁性。 将研究0至26 GHz测量电流对金属（有和没有磁性杂质）和半导体中退相干的影响。 在各种介观样品的热力学电子温度的测量将使用SQUID噪声温度计技术，以检查最近的理论预测，热力学可能会打破在小设备。 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。 参与该计划的研究生将学习如何使用现代制造技术制造各种量子设备，使用最先进的技术测量这些设备，并将理解广泛的固态理论。 所有这些技能都是在工业、政府或大学事业中取得成功所必需的。%当元件的尺寸减小到几微米以下时，所有电路的低温特性都可以显著改变。 电子干涉和电荷量子化等量子效应是这些器件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器件，以帮助推动微电子行业的持续进步。 许多提出的新设备需要长的电子相干时间，以最大限度地提高信号，但大多数纳米级电路只表现出0.05至10纳秒之间的相干时间。 这项研究的重点是了解控制小型电路中相位相干时间的基本物理学，希望我们能够找到增加这一时间的方法。 我们将系统地探索小量子系统在比相位相干时间短得多和长得多的时间尺度上的相位相干输运性质，试图理解我们是否可以操纵量子态而不引起退相干。 参与该计划的研究生将接受必要的培训，成为下一代的微电子科学家。 他们将学习如何使用现代制造技术制造各种量子器件，并使用最先进的技术测量这些器件。 所有这些技能都是必要的，以成为成功的工业，政府或大学的职业生涯。

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.