Mesoscopic Quantum Critical Regimes and Disorder-Driven Deconfinement

介观量子临界状态和无序驱动的解禁

• 批准号: 0703992
• 负责人: Ganpathy Murthy
• 金额: $ 30万
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-12-15 至 2011-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0703992&HistoricalAwards=false
• 关键词: Mesoscopic; Quantum; Critical; Regimes; Disorder

TECHNICAL SUMMARY:This award supports theoretical research and education on materials and systems in which disorder and interactions conspire to create novel states with strong quantum fluctuations. In bulk systems strong quantum fluctuations are characteristic of the quantum critical regime near the bulk quantum phase transition.Mesoscopic systems offer zero-dimensional analogs of bulk quantum phase transitions which can be studied under controlled conditions. The research builds on the PI's past work and is focused on the nature of the ground and low-lying excited states, the signatures of quantum criticality in transport properties, and on the crossover between mesoscopic quantum critical regimes and bulk quantum criticality. The successful completion of this research will provide the fundamental understanding to enable the creation, control, and characterization of mesoscopic systems with strong quantum fluctuations.Recently, tremendous progress has been made in identifying deconfined phases and critical points in two-dimensional quantum antiferromagnets. Such deconfined regimes appear difficult to access in realistic lattice spin systems, and are probably unstable to quenched disorder. The PI finds that deconfinement is generically possible in disordered multicomponent quantum Hall systems, and is in fact driven by quenched disorder. The fundamental reason is the spin-charge relation of the lowest Landau level, which forbids hedgehogs/monopoles by local charge conservation. In turn, the suppression of these topological objects leads to deconfinement. Smooth disorder is needed to restore the broken symmetry of the quantum Hall ferromagnet and push the system into a deconfined state. The "nu" = 1 bilayer system, which experimentally shows dissipation at the lowest measured temperatures, is a good candidate for such a deconfined state. The primary focus of this research thrust will be to investigate the occurrence and properties of phases with gapped fermions and deconfined spinons. The successful completion of this research will result in a deeper understanding of both deconfined phases and multicomponent quantum Hall systems.The education of a postdoc and a graduate student in the latest techniques of mesoscopic and strongly correlated physics is an integral part of this proposal.NON-TECHNICAL SUMMARY:This award supports theoretical research and education on materials and systems that will study the nature of phase transitions which occur at the absolute zero of temperature and are believed to be able to affect the properties of materials at temperatures up to room temperature and possibly beyond. Unlike more familiar phase transitions, like the transformation of water to steam, in which thermal fluctuations are responsible for driving the system through the transformation, quantum phase transitions are driven by a fundamental principle of quantum mechanics due to Heisenberg known as the uncertainty principle. A theme of this research project is to better understand these unusual phase transitions and the affect that they have on the properties, particularly electronic properties, of materials and material systems, and the new states of matter that may occur, through the study of systems that may be particularly susceptible to the scrutiny of experiment and purposeful control. Specific mesoscopic systems involving, for example, quantum dots and nanoscale phenomena involving electrons trapped in semiconductors and exposed to large magnetic fields are identified as promising avenues of inquiry and hold potential for new discoveries. A thrust of the research is to understand how deviations from perfect order affect quantum phase transitions and the nature of the states of matter involved in the transformation.This is fundamental research that is distant from immediate technological application, but it lays the intellectual foundations that may someday support advanced technologies with devices that exploit quantum mechanical principles for their operation, for example quantum computers.The education of a postdoc and a graduate student in the latest techniques of mesoscopic and strongly correlated physics is an integral part of this proposal.

技术摘要：该奖项支持有关材料和系统的理论研究和教育，在这些材料和系统中，疾病和互动共同创造了具有巨大量子波动的新型状态。在整体系统中，强量子波动是大体量子相变附近量子临界状态的特征。尺度系统提供的零量量子相变的零维类似物可以在受控条件下研究。该研究基于PI过去的工作，并集中在地面和低洼的激发状态，运输特性中量子关键的签名以及介质量子临界方案和批量量子关键方面之间的交叉。这项研究的成功完成将提供基本的理解，以实现具有强大量子波动的介质系统的创建，控制和表征。实际上，在识别二维量子量子抗铁磁铁中识别解剖阶段和关键点方面取得了巨大进步。在逼真的晶格旋转系统中，这种脱合性的政权似乎很难访问，并且可能对淬火疾病不稳定。 PI发现，在无序的多组分量子室系统中，脱糊化是可能的，实际上是受淬火疾病驱动的。 基本原因是最低的Landau水平的旋转电荷关系，该关系禁止通过局部电荷保护来刺猬/单极。反过来，这些拓扑对象的抑制会导致解解。需要平滑障碍来恢复量子大厅铁磁体的断裂对称性，并将系统推入污染状态。 “ NU” = 1双层系统，该系统在最低测得的温度下实验表明耗散，是这种脱糊状状态的良好候选者。这项研究推力的主要重点是研究具有张开的费米子和脱糊状旋子的相位的发生和特性。这项研究的成功完成将导致对脱凝时的阶段和多组分量子厅系统的更深入了解。对介质的最新技术和研究生的教育，并在中学和强度相关的物理学的最新技术中，是该提案的重要组成部分。该提案的一部分是该奖项的最初奖励，该奖项对阶段和阶段进行了研究，该奖项对材料的阶段和阶段进行了研究，该阶段是对材料的阶段和阶段的启动。据信能够在温度到室温甚至可能以外的温度下影响材料的特性。与更熟悉的相变（例如水向蒸汽的转化），热波动是负责通过转化推动系统的量子相变的，量子相变的驱动是由量子力学的基本原理驱动，因为海森堡被称为不确定原理。该研究项目的一个主题是通过研究可能特别容易受到实验和有目的控制的系统的审查，更好地了解材料和材料系统的特性，尤其是电子特性，以及可能发生的物质的新状态。涉及涉及量子点和纳米级现象的特定介观系统涉及被困在半导体中并暴露于大型磁场的电子的纳米级现象是有希望的查询途径，并具有新发现的潜力。这项研究的作用是了解与转型中有关物质状态的偏差如何影响量子相过渡的性质。这是远离直接技术应用的基础研究，但它可以将有一天支持的设备与量子机械级的量子进行量化的量化技术相关，例如，逐步启动了量子的量化技术，例如，逐步逐步进行了量子的教育。介质和强烈相关的物理是该提案不可或缺的一部分。