Quantum Phase Transitions: Disorder, Dynamics, and Frustration

量子相变：无序、动力学和挫败感

• 批准号: 0906566
• 负责人: Thomas Vojta
• 金额: $ 32.4万
• 依托单位: Missouri University of Science and Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0906566&HistoricalAwards=false
• 关键词: Quantum; Phase; Transitions; Disorder; Dynamics

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).TECHNICAL SUMMARYThis award supports theoretical research and education on correlated quantum materials and nanostructures. These show a rich variety of novel phenomena due to the competition between quantum fluctuations, various interactions, quantum confinement and disorder. The quantum phase transitions that separate the different ground state phases in these systems play an important role for at least two reasons. On the one hand, their peculiar properties can control large parts of parameter space. On the other hand, they provide a novel perspective for understanding the entire phase diagram of a complex quantum system which is complimentary to traditional perturbative approaches.The major objective of this proposal is to explore quantum phase transitions in a variety of quantum materials, concentrating on three areas:1. Quantum phase transitions and quenched disorder: The PI will focus on disorder effects at first-order quantum phase transitions including those of the order-disorder type as well as transitions between competing ground state orders. Motivated by recent interesting experiments in cerium-palladium-ruthenium systems and nickel-vanadium systems, the PI will analyze the disordered itinerant ferromagnetic transition.2. Dynamics and transport at quantum critical points: The PI will study the transport properties at the superconductor-metal transition in ultrathin MoGe and Niobium nanowires. The PI will develop a theory of electronic transport in the magnetic Griffiths phases of metallic ferromagnets and antiferromagnets.3. Quantum phase transitions in geometrically frustrated magnets: The PI plans to investigate how the interplay between degeneracy, fluctuations and disorder leads to novel phases in geometrically frustrated quantum magnets, and he will study the quantum phase transitions between these phases.To carry out the research, the PI will use a combination of analytical techniques, including mean-field theory, perturbative and strong-disorder renormalization groups, and computer simulations, including classical and quantum Monte-Carlo methods, numerical renormalization group.Undergraduate students will be involved in the research. To help close the gap between classroom and research, the PI intends to complement his computational physics course, which has been instrumental for attracting undergraduates, with a seminar course on high-performance scientific computing aimed at bringing together the interested Missouri S&T students from various disciplines. The PI also aims to establish a series of ?Nobel Prize talks? to be given each fall after the Physics Nobel Prize has been announced. These talks will give an elementary introduction into the physics behind the prize, at a level accessible for non-science majors and high-school students. This series would help disseminate the excitement of science to a broader audience.NON-TECHNICAL SUMMARYThis award supports theoretical research and education on an important aspect of materials in which electrons interact with each other particularly strongly. These materials often exhibit many different phases such as different kinds of magnetism and superconductivity ? an electronic state of matter which exhibits no resistance to the flow of electricity. These phases may be separated by an unusual kind of phase transition which takes place at the absolute zero of temperature called a quantum phase transition. The points that separate phases can control the electronic properties of materials over a wide range of temperature. The PI will use advanced theoretical methods and computer simulations to study the effect of imperfections in the crystal lattice on these quantum critical points and the properties of the electronic states near quantum critical points that separate novel states of matter. The research will contribute to our understanding of an interesting and growing class of materials that display new electronic states of matter and new phenomena that provide the intellectual foundations for possible new electronic device technologies.Undergraduate students will be involved in the research. To help close the gap between classroom and research, the PI intends to complement his computational physics course, which has been instrumental for attracting undergraduates, with a seminar course on high-performance scientific computing aimed at bringing together the interested Missouri S&T students from various disciplines. The PI also aims to establish a series of ?Nobel Prize talks? to be given each fall after the Physics Nobel Prize has been announced. These talks will give an elementary introduction into the physics behind the prize, at a level accessible for non-science majors and high-school students. This series would help disseminate the excitement of science to a broader audience.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。技术概述该奖项支持相关量子材料和纳米结构的理论研究和教育。由于量子涨落、各种相互作用、量子限制和无序之间的竞争，这些显示了丰富多样的新现象。在这些系统中分离不同基态相的量子相变至少出于两个原因而起重要作用。一方面，它们的特殊性质可以控制参数空间的大部分。另一方面，它们为理解复杂量子系统的整个相图提供了一个新的视角，这是对传统微扰方法的补充。本计划的主要目标是探索各种量子材料中的量子相变，主要集中在三个方面：1.量子相变和猝灭无序：PI将专注于一级量子相变的无序效应，包括有序-无序类型以及竞争基态有序之间的转变。受到最近在铈-钯-钌系统和镍-钒系统中有趣实验的启发，PI将分析无序巡游铁磁转变。量子临界点的动力学和输运：PI将研究超导体-金属转变时的输运性质，如钼锗和铌纳米线。该PI将开发一个理论的电子输运在磁性格里菲斯阶段的金属铁磁体和反铁磁体。几何受抑磁体中的量子相变：该研究员计划研究简并、涨落和无序之间的相互作用如何导致几何受抑量子磁体中的新相，并研究这些相之间的量子相变。为了进行研究，该研究员将结合分析技术，包括平均场理论、微扰和强无序重整化群、和计算机模拟，包括经典和量子蒙特-卡罗方法，数值重整化群。本科生将参与研究。为了帮助缩小课堂和研究之间的差距，PI打算补充他的计算物理课程，这是有助于吸引本科生，高性能科学计算的研讨会课程，旨在汇集感兴趣的密苏里州ST学生来自不同学科。PI还旨在建立一系列？诺贝尔奖演讲？在每年秋天诺贝尔物理学奖宣布后颁发。这些讲座将对奖项背后的物理学进行初步介绍，非科学专业和高中生都可以参加。这一系列将有助于向更广泛的受众传播科学的兴奋。非技术总结该奖项支持理论研究和教育的一个重要方面的材料，其中电子相互作用特别强烈。这些材料往往表现出许多不同的相，如不同种类的磁性和超导性？物质的一种电子状态，对电流没有阻力。这些相可以被一种不寻常的相变分开，这种相变发生在绝对零度，称为量子相变。分离相的点可以在很宽的温度范围内控制材料的电子特性。PI将使用先进的理论方法和计算机模拟来研究晶格中的缺陷对这些量子临界点的影响，以及量子临界点附近的电子态的性质，这些量子临界点分离了新的物质状态。这项研究将有助于我们了解一个有趣的和不断增长的材料，显示新的电子状态的物质和新的现象，提供可能的新的电子器件技术的知识基础。本科生将参与研究。为了帮助缩小课堂和研究之间的差距，PI打算补充他的计算物理课程，这是有助于吸引本科生，高性能科学计算的研讨会课程，旨在汇集感兴趣的密苏里州ST学生来自不同学科。PI还旨在建立一系列？诺贝尔奖演讲？在每年秋天诺贝尔物理学奖宣布后颁发。这些讲座将对奖项背后的物理学进行初步介绍，非科学专业和高中生都可以参加。这一系列将有助于向更广泛的受众传播科学的兴奋。