Unconventional quantum phase transitions

该奖项支持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，材料在绝对零度温度下的量子态会发生突变。这种量子相变是现代物理学的中心概念，对非零温度有影响，并在量子世界中作为普遍的有序原则。然而，它们的行为可能与由热波动（如冰的融化或水的沸腾）驱动的更常见的相变有很大的不同。该项目将探索磁性和超导材料、人造纳米结构和原子气体中的量子相变。主要目标是了解这些转变如何在广泛的外部条件下控制材料在低温下的性能。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，并通过每年一次的“诺贝尔奖座谈会”（Nobel Prize Colloquia），对奖项背后的科学进行初步介绍，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执行这项研究，包括重整化组计算和大规模蒙特卡罗模拟。由于量子相干性、相关性、自旋轨道耦合和无序性的相互作用，量子多粒子系统显示出丰富的相图。不同基态之间的量子相变概念是现代凝聚态物理学中最重要的概念之一，因为量子相变可以在宽参数区域内控制材料的性质，并且可以作为相图的通用排序原则。最近的研究表明，许多量子相变并不遵循热转变的已建立的摄动朗道-金兹堡-威尔逊范式。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将研究超越Landau-Ginzburg-Wilson范式的几种量子相变，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朗道-金兹堡-威尔逊情景的新范式来改变我们对量子相变的理解。这项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，并将提出新的实验。此外，这些活动将培训青年科学家，改善教育和研究基础设施，并帮助广大受众参与科学和技术。

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.