Unconventional quantum phase transitions

非常规量子相变

• 批准号: 1506152
• 负责人: Thomas Vojta
• 金额: $ 33.9万
• 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: 2016
• 资助国家: 美国
• 起止时间: 2016-01-15 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506152&HistoricalAwards=false
• 关键词: Unconventional; quantum; phase; transitions

NONTECHNICAL SUMMARY This award supports theoretical and computational research into the quantum properties of materials as well as education and outreach activities. If external conditions such as pressure or magnetic field vary, the quantum state of a material at the absolute zero of temperature can undergo abrupt transformations. Such quantum phase transitions are a central concept of modern physics, have consequences for nonzero temperatures, and serve as universal ordering principle in the quantum world. However, their behavior can differ greatly from that of more common phase transitions driven by thermal fluctuations such as the melting of ice or the boiling of water.This project will explore quantum phase transitions in magnetic and superconducting materials, in man-made nanostructure, and in atomic gases. The main goal is to understand how these transitions control materials properties at low temperatures over broad ranges of external conditions. In addition, activities supported by this award will contribute to training young scientists, improve the computational education and research infrastructure, and help engage broad audiences in science and technology by means of yearly "Nobel Prize Colloquia" that give elementary introductions into the science behind the prizes.TECHNICAL SUMMARYThis award supports research in theoretical and computational quantum condensed matter physics and associated education and outreach activities. The scientific objective is to explore unconventional quantum phase transitions in correlated electron materials, ultracold atomic gases, quantum nanostructures, and other types of quantum matter. The PI will employ a combination of analytical and computational methods to perform this research including renormalization group calculations and large-scale Monte-Carlo simulations.Quantum many-particle systems display rich phase diagrams due to the interplay between quantum coherence, correlations, spin-orbit coupling, and disorder. The concept of a quantum phase transitions between different ground states is among to the most important of modern condensed matter physics because a quantum phase transition can control materials properties in wide parameter regions, and serves as universal ordering principle for the phase diagram.Recent research has shown that many quantum phase transitions do not follow the established perturbative Landau-Ginzburg-Wilson paradigm for thermal transitions. As a result, many quantum phase transitions observed in nature are still poorly understood, and sometimes not even the correct theoretical framework is known. The PI will therefore investigate several classes of quantum phase transitions beyond the Landau-Ginzburg-Wilson paradigm, focusing on four areas, (i) first-order quantum phase transitions and emerging criticality, (ii) microscopic probes in strongly disordered quantum systems, (iii) Berry phases and dissipation at impurity quantum phase transitions, (iv) topological disorder, correlations, and criticality.This research will transform our understanding of quantum phase transitions by helping to establish novel paradigms that complement the traditional Landau-Ginzburg-Wilson scenario. The research will also explain experimental results in transition metal and f-electron compounds as well as ultracold gases, and it will suggest new experiments.In addition, the activities will train young scientists, improve the education and research infrastructure, and help engage broad audiences in science and technology.

该奖项支持对材料量子特性的理论和计算研究以及教育和推广活动。如果外部条件如压力或磁场发生变化，材料在绝对零度下的量子态会发生突变。这种量子相变是现代物理学的核心概念，对非零温度有影响，并作为量子世界中的普遍有序原则。然而，它们的行为可能与由热波动（例如冰的融化或水的沸腾）驱动的更常见的相变有很大不同。该项目将探索磁性和超导材料、人造纳米结构和原子中的量子相变。气体。主要目标是了解这些转变如何在低温下在广泛的外部条件下控制材料性能。 此外，该奖项支持的活动将有助于培训年轻科学家，改善计算教育和研究基础设施，并通过每年的“诺贝尔奖座谈会”，帮助广大受众参与科学和技术该奖项支持理论和计算量子凝聚态物理学的研究以及相关的教育和推广。活动科学目标是探索相关电子材料，超冷原子气体，量子纳米结构和其他类型的量子物质中的非常规量子相变。PI将采用分析和计算方法相结合的方法来进行这项研究，包括重整化群计算和大规模的蒙特-卡罗模拟。量子多粒子系统显示丰富的相图，由于量子相干性，相关性，自旋轨道耦合和无序之间的相互作用。不同基态之间的量子相变是现代凝聚态物理中最重要的概念之一，因为量子相变可以在很宽的参数范围内控制材料的性质，并且是相图的普遍有序性原则，最近的研究表明，许多量子相变并不遵循已经建立的热相变的微扰Landau-Ginzburg-Wilson范式。因此，在自然界中观察到的许多量子相变仍然知之甚少，有时甚至不知道正确的理论框架。因此，PI将研究Landau-Ginzburg-Wilson范式之外的几类量子相变，重点关注四个领域，（i）一阶量子相变和新兴临界性，（ii）强无序量子系统中的微观探针，（iii）杂质量子相变时的Berry相和耗散，（iv）拓扑无序，相关性，和临界性。这项研究将通过帮助建立补充传统兰道-金斯伯格-威尔逊场景的新范式来改变我们对量子相变的理解。该研究还将解释过渡金属和f-电子化合物以及超冷气体的实验结果，并提出新的实验建议。此外，该活动还将培训年轻科学家，改善教育和研究基础设施，并帮助吸引广大受众参与科学和技术。