Experimental Studies of Persistent Currents in Normal Metals

普通金属中持续电流的实验研究

• 批准号: 1106110
• 负责人: Jack Harris
• 金额: $ 38.1万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1106110&HistoricalAwards=false
• 关键词: Experimental; Studies; Persistent; Currents; Normal

****TECHNICAL ABSTRACT****Persistent currents are one of the most dramatic phenomena of mesoscopic physics. The notion of a disipationless electrical current flowing through a resistor is quite counterintuitive, although at its simplest, it is a manifestation of the same phenomena that allows isolated atoms to posses orbital angular momentum in their electronic ground state. In mesoscopic solid-state devices, a considerable body of theoretical work suggests that persistent currents may be quite sensitive to a variety of many body effects. However until recently, the reliable measurement of persistent currents was technically very challenging. This project will use newly developed detection techniques to measure persistent currents in regimes where many body effects are expected to be dominant. Specifically, micromechanical torsional magnetometry will be used to measure the average current in diffusive metal rings at low magnetic fields, where it has been predicted that the same interaction effects that give rise to BCS superconductivity can lead to dramatically enhanced persistent current in the normal state. In addition, the same techniques will be used to measure the persistent current in high-mobility two dimensional electron gases, both in low magnetic fields (where the persistent current can be used to study the spectra of chaotic or integrable samples), and at high magnetic fields, where the persistent current can be used to probe the statistics of the quasiparticles. This project will support the training of a Ph.D. student, who will learn a variety of technical skills, including semiconductor micro- and nano-fabrication, cryogenics, fiber optics, micromechanics, and ultrasensitive measurement techniques.****NON-TECHNICAL ABSTRACT****One of the most striking results of applying the theory of quantum mechanics to an entire electrical circuit is the prediction that, despite the electrical resistance of the circuit, electrical current can flow perpetually through it without gaining or losing energy. This phenomenon is known as persistent current, and is directly analogous to the more familiar orbits of electrons around the nucleus of an atom. However in the setting of an electrical circuit, the orbitals which produce the persistent current are flowing through metal wires which are ten thousand times longer than a single atom. Until recently it was considered nearly impossible to measure these currents reliably, but this project will use newly-developed measurement techniques to study persistent currents in a variety of different materials. This goal is motivated by the theoretical prediction that the basic properties of the persistent current (for example, its size and the direction of its flow) can tell us a great deal about two exotic but extremely important phenomena: superconductivity (in which a metal loses all resistance to electrical currents) and the fractional quantum Hall state (in which electrons in a semiconductor bind together with a magnetic field to create particles that have no analog in nature). This project will advance our understanding of these phenomena, and will also result in new types of instruments for studying the behavior of electrons in small, isolated samples. This project will support the training of a Ph.D. student, who will learn a variety of technical skills, including semiconductor micro- and nano-fabrication, cryogenics, fiber optics, micromechanics, and ultrasensitive measurement techniques.

* 技术摘要 * 持续电流是介观物理学中最引人注目的现象之一。无耗散电流流过电阻器的概念是非常违反直觉的，尽管在最简单的情况下，它是允许孤立原子在其电子基态中消除轨道角动量的相同现象的表现。在介观固态器件中，相当多的理论工作表明，持续电流可能对多种体效应非常敏感。然而，直到最近，持续电流的可靠测量在技术上还是非常具有挑战性的。该项目将使用新开发的探测技术，在许多身体效应预计占主导地位的情况下测量持续电流。具体而言，微机械扭转磁力将被用来测量在低磁场下的扩散金属环的平均电流，其中已经预测，引起BCS超导性的相同的相互作用效应可以导致在正常状态下显著增强的持续电流。此外，相同的技术将被用来测量高迁移率的二维电子气体中的持续电流，无论是在低磁场（持续电流可用于研究混沌或可积样品的光谱），并在高磁场，持续电流可用于探测准粒子的统计。该项目将支持培养一名博士。学生，谁将学习各种技术技能，包括半导体微米和纳米制造，低温，光纤，微机械和超灵敏测量技术。将量子力学理论应用于整个电路的最显著的结果之一是预测，尽管电路的电阻，电流可以永远流过它而不会获得或损失能量。这种现象被称为持续电流，它直接类似于我们更熟悉的电子围绕原子核的轨道。然而，在电路的设置中，产生持续电流的轨道流过比单个原子长一万倍的金属线。直到最近，人们还认为几乎不可能可靠地测量这些电流，但该项目将使用新开发的测量技术来研究各种不同材料中的持续电流。这一目标的动机是理论预测，持续电流的基本性质（例如，它的大小和流动的方向）可以告诉我们很多关于两个奇异但极其重要的现象：超导（其中金属对电流失去所有电阻）和分数量子霍尔态（其中半导体中的电子与磁场结合在一起，产生本质上没有类似物的粒子）。该项目将促进我们对这些现象的理解，并将导致研究小的孤立样品中电子行为的新型仪器。该项目将支持培养一名博士。学生，谁将学习各种技术技能，包括半导体微和纳米制造，低温，光纤，微机械和超灵敏测量技术。