Unconventional Quantum Phase Transitions

非常规量子相变

• 批准号: 1205803
• 负责人: Thomas Vojta
• 金额: $ 37.99万
• 依托单位: Missouri University of Science and Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1205803&HistoricalAwards=false
• 关键词: Unconventional; Quantum; Phase; Transitions

TECHNICAL SUMMARYThis award supports theoretical and computational research and education to advance understanding of quantum phase transitions and broaden it beyond the Landau-Ginzburg-Wilson paradigm. The PI will explore several classes of unconventional quantum phase transitions, focusing on four separate but related areas.1. Strong-disorder quantum phase transitions: Motivated by experiments on nitrogen-vanadium, cerium-palladium-rhodium, and strontium-calcium ruthenate compounds, the PI aims to develop a theory of rare region effects at itinerant ferromagnetic quantum phase transitions. He will also study the influence of randomness on first-order quantum phase transitions as well as the effects of disorder correlations.2. Novel phases and transitions in layered systems: The PI will investigate the unusual phases and transitions emerging in randomly and quasi-periodically layered superconductors and superfluids that can be produced in ultracold gases or nano-structured materials.3. Dynamics and transport at quantum critical points: The PI will study the conductance of superconducting molybdenum germanium and niobium nanowires at the superconductor-metal quantum phase transition. He will also investigate electronic transport in ferromagnetic Griffiths phases.4 Berry phases in impurity problems and percolation transitions: The PI plans to analyze the effects of Berry phases on the quantum-to-classical mapping of impurity quantum phase transitions as well as their effects on percolation transitions of rotors and spins.A combination of analytical techniques and computer simulation will be used to carry out the research.This award also supports efforts to establish a series of "Nobel Prize talks" to be given each fall after the prizes in physics, chemistry and physiology or medicine have been announced. The talks in this series will be coordinated between the Missouri S&T departments of physics, chemistry and biological sciences. They will give elementary introductions into the science behind the prize. These talks will expand the successful series of talks on the physics prize that the PI has organized since 2007. The proposed work will also enhance the research and education infrastructure at Missouri S&T, as the Pegasus computer cluster designed and built and built by the PI becomes a hub of computational research in the Physics Department. NON- TECHNICAL SUMMARYThis award supports theoretical and computational research and education with the aim to advance understanding of a type of phase transition that occurs in materials at the absolute zero of temperature called a quantum phase transition. Unlike familiar phase transitions, for example the transformation of water to steam, which are driven by thermal fluctuations, quantum phase transitions are driven by quantum mechanical fluctuations, a consequence of the Heisenberg uncertainty principle. Quantum phase transitions are important because their influence can extend to temperatures, possibly as high as room temperature and beyond, and profoundly change the behavior of electrons in materials. This has consequences on the way electrons organize themselves into states of matter, such as magnetism and superconductivity, and other exotic states that have been predicted to occur in materials where electrons interact strongly with each other. The perhaps less familiar state of superconductivity has the unusual feature of being able to conduct electricity without losing energy to dissipation. This leads to potential applications in power transmission. Known superconducting materials only exhibit superconductivity at frigid temperatures, some as high as temperatures where atmospheric gases like oxygen and nitrogen are liquids. A better understanding of quantum critical phenomena may help discover materials that exhibit superconductivity at much higher temperatures. The rigorous description of quantum phase transitions lies outside the standard theory of phase transitions. This research has potential to open new areas in the study of phase transitions. Quantum phase transitions may also have important consequences for efforts to develop quantum computers which are based on the manipulation of quantum mechanical states, and nanoscale technologies involving elements that are some tens of thousands of times smaller than the diameter of a human hair.This award also supports efforts to establish a series of "Nobel Prize talks" to be given each fall after the prizes in physics, chemistry and physiology or medicine have been announced. The talks in this series will be coordinated between the Missouri S&T departments of physics, chemistry and biological sciences. They will give elementary introductions into the science behind the prize. These talks will expand the successful series of talks on the physics prize that the PI has organized since 2007. The proposed work will also enhance the research and education infrastructure at Missouri S&T, as the Pegasus computer cluster designed and built and built by the PI becomes a hub of computational research in the Physics Department.

该奖项支持理论和计算研究和教育，以促进对量子相变的理解，并将其扩展到Landau-Ginzburg-Wilson范式之外。PI将探索几类非常规的量子相变，专注于四个独立但相关的领域。 强无序量子相变：受氮钒，铈钯铑和锶钙铼酸盐化合物实验的启发，PI旨在发展巡回铁磁量子相变的稀有区域效应理论。他还将研究随机性对一阶量子相变的影响以及无序相关性的影响。2.分层系统中的新相和转变：PI将研究随机和准周期性分层超导体和超流体中出现的不寻常的相和转变，这些超导体和超流体可以在超冷气体或纳米结构材料中产生。量子临界点的动力学和输运：PI将研究超导钼锗和铌纳米线在超导体-金属量子相变时的电导。他还将研究铁磁Griffiths相中的电子输运。4杂质问题和渗滤过渡中的Berry相：PI计划分析Berry相位对量子到杂质量子相变的经典映射以及它们对转子和自旋的渗流相变的影响。分析技术和计算机模拟相结合将用于开展研究。该奖项还支持每年秋天在物理学、化学、生理学或医学奖项公布后举办一系列“诺贝尔奖讲座”。在这个系列的会谈将协调之间的物理，化学和生物科学的密苏里州科技部门。他们将对奖项背后的科学进行初步介绍。这些讲座将扩大PI自2007年以来组织的关于物理学奖的成功系列讲座。拟议的工作还将加强研究和教育基础设施在密苏里州ST，作为飞马座计算机集群设计和建造和建造的PI成为计算研究的中心在物理系。该奖项支持理论和计算研究和教育，旨在促进对绝对零度下材料中发生的一种相变的理解，称为量子相变。与常见的相变不同，例如由热涨落驱动的水到蒸汽的转变，量子相变是由量子力学涨落驱动的，这是海森堡不确定性原理的结果。量子相变很重要，因为它们的影响可以延伸到温度，可能高达室温或更高，并深刻地改变材料中电子的行为。这对电子将自己组织成物质状态的方式产生了影响，例如磁性和超导性，以及其他被预测会发生在电子彼此强烈相互作用的材料中的奇异状态。 也许不太熟悉的超导状态具有不寻常的特征，即能够导电而不会损失能量。这导致在电力传输中的潜在应用。已知的超导材料仅在极低的温度下表现出超导性，有些温度高至大气气体如氧气和氮气为液体的温度。 更好地理解量子临界现象可能有助于发现在更高温度下表现出超导性的材料。 量子相变的严格描述在标准相变理论之外。这一研究有可能为相变研究开辟新的领域。量子相变也可能对开发基于量子力学状态操纵的量子计算机以及涉及比人类头发直径小数万倍的元素的纳米级技术的努力产生重要影响。该奖项还支持建立一系列“诺贝尔奖讲座”的努力，这些讲座将在每年秋季物理学奖之后举行，化学和生理学或医学已经宣布。在这个系列的会谈将协调之间的物理，化学和生物科学的密苏里州科技部门。他们将对奖项背后的科学进行初步介绍。这些讲座将扩大PI自2007年以来组织的关于物理学奖的成功系列讲座。拟议的工作还将加强研究和教育基础设施在密苏里州ST，作为飞马座计算机集群设计和建造和建造的PI成为计算研究的中心在物理系。