CAREER: Theories of Gapless Quantum Matter Beyond Quasiparticles

该职业奖支持理论凝聚态物理的综合研究、推广和教育计划。在足够低的温度下，一些材料可以表现出超导性，这是一种物质状态，电子自组织成一种可以导电而不耗散的合作状态。超导体在能量存储和传输、医疗诊断和量子计算等领域的应用，有可能改变量子技术和人类社会的未来，因此推动了对高温超导性的研究。然而，高温超导的微观原因仍然是个谜。这项研究将集中在一类非常规金属上，它们是高温超导体的“母态”。不像铜这样的简单金属，每次只考虑一个电子就能有效地理解其性质，这些非常规金属被最好地描述为一种集体量子流体，其中电子彼此之间在很远的距离上强烈纠缠。这项研究将开发描述这些纠缠电子液体所需的技术框架。这将为确定高温超导起源的关键微观机制铺平道路。PI和他的团队将在不同子领域的最新理论发展的基础上开发新的理论方法。PI将开发精确的理论方法，这些方法具有预测能力，可以在实验室的真实材料实验中进行测试。由此产生的结果将影响对数万亿纠缠电子的集体量子力学特性的基本理解，并可能有助于指导未来寻找具有奇异特性的新材料。这些方法和结果将向更广泛的社会传播。与此同时，PI将发起和参与各种教育和外联活动。尽管量子物理学对新技术的发展产生了影响，这些新技术已成为每个人日常生活的一部分，但它以难以接近而闻名。PI将开始一个新的播客系列，它将主持与各种知名研究人员的非正式讨论，让学生和公众对量子材料的物理学感到兴奋。PI还将为高中科学教师组织研讨会，共同制定引人入胜的课程计划。PI将指导本科生和研究生进行原创研究，并撰写教学文章，旨在培养他们在与研究活动相一致的新科学发展方面的能力。该职业奖支持理论凝聚态物理的综合研究，推广和教育计划。这项研究的目标将是解决高温超导的长期谜团的一些关键方面。具体来说，重点将放在量子材料中出现的超导性的不寻常的无间隙金属相上。实验表明，在强相关的金属中，电子的量子运动在长距离中受到阻碍和纠缠，微观自由度，即电子和声子，彼此之间强烈纠缠。这项研究活动将开发新颖的、非摄动的理论方法来解决电子液体与其他集体自由度纠缠的问题，以揭示无间隙量子多体系统的普遍方面。PI将制定新的方法来研究相互作用的无间隙相，这些相不依赖于存在定义良好的类电子（“准粒子”）激发。为了解决它们的非寻常动力学，PI将开发新的理论技术，这些技术是基于研究受挫磁体的技术进步，混沌量子多体系统中的热化，以及不受费米子“符号问题”影响的数值精确算法。PI将建立在以下假设的基础上：(i)相互作用的受挫液体为包括量子涨落的影响和描述以前未探索的无间隙相提供了一个非平凡的起点；（ii）对于具有一般相互作用的足够“混沌”的模型，金属中电输运的传统理论可能会在广泛的中间温度范围内失效。PI还将利用最近在高度可控的涡流系统方面取得的突破，重点关注使用数值精确方法与低能量声子耦合的窄电子带问题。分析这些问题将提供一个重要的概念框架，将大量现有的高温超导体实验数据联系在一起，并有助于指导寻找显示类似现象的新材料。PI的教育和外展活动与研究协同结合。PI将启动一个新的播客系列，由不同的知名研究人员组成，以提高公众和学生对该领域令人兴奋的认识。PI将指导本科生和研究生进行原创性研究，并撰写旨在训练他们适应与研究活动相一致的新科学发展的教学文章。通过STEM教师计划，PI将利用康奈尔大学现有的基础设施，为高中科学教师组织一系列研讨会，共同制定引人入胜的课程计划。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis CAREER award supports an integrated research, outreach, and education program in theoretical condensed matter physics. At sufficiently low temperature some materials can exhibit superconductivity, a state of matter where electrons self-organize into a cooperative state which can conduct electricity without dissipation. The search for superconductivity at high temperatures is driven by the potential of superconductors to transform the future of quantum technologies and human society, with applications in energy storage and transmission, medical diagnostics, and quantum computing. However, the microscopic reasons for superconductivity at high temperature remain mysterious. The research will be focused on a class of unconventional metals, which are the “parent” states for high temperature superconductors. Unlike simple metals such as copper, whose properties can be effectively understood by considering the electrons one at a time, these unconventional metals are best described as a collective quantum fluid where the electrons are strongly entangled over long distances with one another. This research will develop the required technical framework to describe these entangled electronic liquids. This will pave the way for identifying the key microscopic mechanisms responsible for the origin of superconductivity at high temperatures.The PI and his group will develop new theoretical methods building on recent theoretical developments across different subfields. The PI will develop exact theoretical methods that have a predictive power that can be tested against experiments on real materials in the laboratory. The resulting outcome will impact the fundamental understanding of the collective quantum mechanical properties of trillions of entangled electrons, and potentially help guide the future search for new materials displaying exotic properties. The methods and results will be disseminated to the wider community.In parallel, the PI will initiate and participate in a variety of educational and outreach activities. Although quantum physics has impact on the development of new technologies that become part of everyone’s daily lives, it has a reputation for being inaccessible. The PI will start a new podcast series, which will host informal discussions with a diverse lineup of well-known researchers, to get students and the general public excited about the physics of quantum materials. The PI will also organize workshops for high school science teachers to co-develop engaging lesson plans. The PI will mentor undergraduate and graduate students in original research, and write pedagogical articles aimed at training them in the new scientific developments aligned with the research activities.TECHNICAL SUMMARYThis CAREER award supports an integrated research, outreach, and education program in theoretical condensed matter physics. The goal of the research will be to address some of the key facets of the long-standing mystery of high-temperature superconductivity. Specifically, the focus will be on the unusual gapless metallic phases out of which superconductivity emerges in quantum materials. Experiments suggest that the quantum motion of electrons is frustrated and entangled over long distances in strongly correlated metals, and the microscopic degrees of freedom, namely electrons and phonons, are strongly intertwined with each other. This research activity will develop novel, non-perturbative theoretical approaches to solve the problem of electronic liquids entangled with other collective degrees of freedom, to expose universal aspects of gapless quantum many-body systems.The PI will formulate new approaches for studying interacting gapless phases that do not rely on the existence of well-defined, electron-like (“quasiparticle”) excitations. To address their non-trivial dynamics, the PI will develop novel theoretical techniques that are based on technical advances in the study of frustrated magnets, thermalization in chaotic quantum many-body systems, and numerically exact algorithms that do not suffer from the fermion “sign problem”. The PI will build on the following conjectures: (i) interacting frustrated liquids offer a non-trivial starting point for including the effects of quantum fluctuations and describing previously unexplored gapless phases; and (ii) the conventional theory for electrical transport in metals can break down over a wide range of intermediate temperatures for sufficiently “chaotic” models with generic interactions. The PI will also exploit recent breakthroughs in the highly controllable moiré systems, focusing on the problem of narrow electronic bands coupled to low-energy phonons using numerically exact methods. Analyzing these questions will offer an important conceptual framework for tying together a vast amount of existing experimental data on high-temperature superconductors, and help direct the search for new materials displaying similar phenomena.The PI’s educational and outreach activities are integrated synergistically with the research. The PI will start a new podcast series with a diverse lineup of well-known researchers to increase awareness about the excitement in the field amongst the general public and students. The PI will mentor undergraduate and graduate students in original research, and write pedagogical articles aimed at training them at the new scientific developments aligned with the research activities. Leveraging existing infrastructure available at Cornell University through the STEM teacher program, the PI will organize a series of workshops for high school science teachers to co-develop engaging lesson plans.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.