Physics of Non-Fermi Liquid Metals

该奖项支持重费米子材料的理论研究，特别关注量子临界性。我们感兴趣的强相关多电子系统处于与自由电子气体的极限没有绝热联系的状态，并且对电子相关的相关非摄动物理的理论理解仍处于非常早期的阶段。PI将研究适合于受控理论研究的模型系统，并可能为其他更复杂的系统提供经验教训。PI将追求四个具体的研究方向：1)重费米子磁序外的量子跃迁：PI将研究从磁性有序的重费米子金属中发生量子跃迁的方法。这项研究的动机是最近对重费米子金属的实验，这些实验表明至少有三种途径可以实现这种转变。另一个动机是阐明重费米子量子临界性的本质。量子临界重费米子中的超导性：PI将研究在近道坍缩量子临界点附近的重费米子金属中是否以及如何产生非常规的超导性。这项工作将利用过去几年在量子临界性方面的进展，超越序参数波动的朗道范式，并将旨在阐明Ce-115和相关系统中量子临界性和超导性之间的相互作用。引力视角下的量子临界性：PI将从反德西特空间中引力的对偶图像中寻求对近道坍缩局部量子临界性的新见解。PI将探索重费米子量子临界点包含时空波动因子分解作为紧急对称性的可能性。非平衡量子临界的涨落和耗散：一个量子临界点很容易被赶出平衡，因为它的尺度不变涨落谱意味着缺乏任何内在的能量尺度。我们将考虑磁性纳米结构的涨落和耗散作为研究非平衡态更大问题的具体背景。该研究项目将吸引博士后、研究生和本科生参与，并将有助于理解可能构成未来技术基础的材料。该奖项支持对一类特殊材料的理论研究和教育。复杂金属材料的发现，具有不寻常的性质，超出了标准的教科书描述的金属，激发了激烈的研究，旨在了解其性质的物理起源。PI将使用先进的理论方法来解决这个问题，重点是阐明在绝对零度下发生的从一种物质状态到另一种物质状态的转变的本质。人们熟悉的水到冰的转变发生在273K（0摄氏度）左右，温度在其中起着重要作用，与之相反，这种转变是由海森堡提出的量子力学基本原理驱动的。PI正在发展一种理论来解释这些转变以及它们所引起的不寻常的温度依赖特性。PI将开发新的理论方法来研究教科书对金属材料的电子状态和电子状态之间转换的描述如何失败，以及物质的新电子状态如何产生。该研究项目将吸引博士后、研究生和本科生参与，并将有助于理解可能构成未来技术基础的材料。

TECHNICAL SUMMARYThis award supports theoretical research on heavy fermion materials with a particular focus on quantum criticality. The strongly correlated many-electron systems of interest are in regimes that are not adiabatically connected to the limit of free-electron gas, and theoretical understanding of the pertinent non-perturbative physics of electron correlations are still at a very early stage. The PI will study model systems which are amenable to controlled theoretical studies and which may provide lessons for other more complex systems. The PI will pursue four specific research directions: 1.) Quantum Transition out of Magnetic Order in Heavy Fermions: The PI will study ways in which quantum transitions can take place from magnetically-ordered heavy fermion metals. This research is motivated by recent experiments in heavy fermion metals, which suggest at least three routes for such transitions. Another motivation is to shed new light on the nature of heavy fermion quantum criticality.2.) Superconductivity in Quantum Critical Heavy Fermions: The PI will study whether and how unconventional superconductivity arises in heavy fermion metals near a Kondo-collapsing quantum critical point. This work will leverage advances of the past few years on quantum criticality beyond the Landau paradigm of order-parameter fluctuations, and will also aim to elucidate the interplay between quantum criticality and superconductivity in Ce-115 and related systems.3.) Quantum Criticality from a Gravitational Perspective: The PI will seek to gain new insights into the Kondo-collapsing local quantum criticality from a dual picture formulated in terms of gravity in an anti-de Sitter space. The PI will explore the possibility that a heavy-fermion quantum critical point contains the factorization of spatial and temporal fluctuations as an emergent symmetry.4.) Fluctuation and Dissipation of out-of-equilibrium Quantum Criticality: A quantum critical point is readily driven out of equilibrium, as its scale-invariant fluctuation spectrum implies the lack of any intrinsic energy scale. We will consider the fluctuations and dissipation of a magnetic nanostructure as a concrete setting to study the larger issues in non-equilibrium.This research project will engage postdoctoral fellows, graduate students, and undergraduate students, and will contribute to the understanding of materials that may form the foundations of future technologies.NON-TECHNICAL SUMMARYThis award supports theoretical research and education on a class of unusual materials. The discovery of complex metallic materials with unusual properties that lie outside the standard textbook description of metals has motivated intense research that aims to understand the physical origins of their properties. The PI will use advanced theoretical methods to attack this problem with a focus on elucidating the nature of a transformation from one state of matter to another that takes place at the absolute zero of temperature. In contrast to the familiar transformation of water to ice that takes place around 273K, or 0C, and in which temperature plays an important role, this transformation is driven by a fundamental principle of quantum mechanics ascribed to Heisenberg. The PI is developing a theory of these transformations and the unusual temperature dependent properties that they induce. The PI will develop new theoretical methods to study how textbook descriptions for the electronic states of metallic materials and for the transformation between electronic states can fail, and how new electronic states of matter can arise. This research project will engage postdoctoral fellows, graduate students, and undergraduate students, and will contribute to the understanding of materials that may form the foundations of future technologies.