Physics of Non-Fermi-Liquid Metals

技术综述：该奖项支持凝聚态物理的理论研究和教育。PI将关注两个相互补充和相互交织的主题：非费米液体行为的起源和量子临界性。一方面，在强关联材料上的实验为传统的固体中电子理论--朗道的费米液体理论的失败提供了充分的证据。理解非费米液体行为的机制是许多悬而未决的基本问题之一。另一方面，一些金属体系已经成为系统研究量子临界的原型材料。对理论的挑战是巨大的，因为临界波动既是集体的，也是量子力学的。也许最紧迫的问题是，基于序参数波动的传统图景是否足够，或者是否必须将固有的量子自由度纳入临界模式。这些问题对于包括重费米子金属、高温超导体和量子纳米结构在内的一系列新型量子材料具有重要意义。提出的研究包括三个具体的方向：1.磁性重费米子的全局相图：在这里，PI将追求这样的概念，即磁性重费米子金属中的量子相不仅由传统的有序参数来表征，而且还由它们的费米面的性质来表征。反铁磁重费米子系统和铁磁重费米子系统都将被考虑，并将讨论量子临界性的含义。巡回受挫量子磁体中的量子相：PI试图通过几何受阻来理解f电子金属中奇异重费米子行为的起源。量子临界性的非平衡方面：PI将研究具有铁磁引线的单电子晶体管的非线性输运和其他非平衡性质，这种晶体管可以通过量子临界点进行调谐。这个项目不仅对纳米结构感兴趣，而且提供了一个理论上可控的环境来探索量子临界的非平衡方面。这个研究项目将吸引初级科学家和本科生，为他们提供高级理论培训。这项研究将促进对电子材料的理解，这些材料对热电、磁信息和自旋电子技术具有潜在的重要意义。非技术概述：该奖项支持凝聚态物理的理论研究和教育。具有不寻常性质的复杂金属材料的发现超出了教科书对金属的标准描述，这推动了旨在了解其性质的物理起源的紧张研究。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物质从一种状态到另一种状态的转变的本质。人们熟悉的水到冰的转变发生在273K或0摄氏度左右，温度在其中起着重要作用，与此不同，这种转变是由海森堡的量子力学基本原理驱动的。PI正在发展一种关于这些转换及其引起的不寻常的温度依赖属性的理论。这项研究项目将邀请初级科学家和本科生，为他们提供高级理论培训。这项研究将促进对电子材料的理解，有助于为可能的新技术，特别是信息和电子设备技术奠定智力基础。

TECHNICAL SUMMARY:This award supports theoretical research and education in condensed matter physics. The PI will focus on two complementary and intertwined subjects: the origins of non-Fermi liquid behavior and quantum criticality. On the one hand, experiments in strongly correlated materials have provided ample evidence for the failure of the conventional theory of electrons in solids, Landau's Fermi liquid theory. Understanding the mechanisms for non-Fermi liquid behavior is one of the fundamental issues with many open questions. On the other hand, a number of metallic systems have emerged as prototype materials in which quantum criticality can be systematically studied. The challenge to theory is enormous, because the critical fluctuations are both collective and quantum mechanical. Perhaps the most pressing question is whether the traditional picture based on order-parameter fluctuations is adequate, or whether inherently quantum degrees of freedom must be incorporated as part of the critical modes. These issues are important for a wide range of novel quantum materials, including heavy fermion metals, high temperature superconductors, and quantum nanostructures. The proposed research is comprised of three specific directions:1. Global phase diagram of magnetic heavy fermions: Here the PI will pursue the notion that quantum phases in magnetic heavy fermion metals are not only characterized by conventional order parameters, but also by the nature of their Fermi surface. Both antiferromagnetic and ferromagnetic heavy fermion systems will be considered, and the implications for quantum criticality will be addressed.2. Quantum phases in itinerant frustrated quantum magnets: The PI seeks to understand the origin of the singular heavy fermion behavior in f-electron metals with geometric frustration.3. Nonequilibrium aspects of Quantum Criticality: The PI will study the nonlinear transport and other non-equilibrium properties of a single-electron transistor with ferromagnetic leads, which can be tuned through a quantum critical point. This project not only is of interest in the context of nanostructures, but also provides a theoretically controlled setting to explore the non-equilibriums aspects of quantum criticality.This research project will engage junior scientists as well as undergraduate students, providing them with advanced theoretical training. The research will advance the understanding of electronic materials that are potentially important for thermoelectric, magnetic information, and spintronic technologies.NON-TECHNICAL SUMMARY:This award supports theoretical research and education in condensed matter physics. 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. This research project will engage junior scientists as well as undergraduate students, providing them with advanced theoretical training. The research will advance the understanding of electronic materials contributing to the intellectual foundations of possible new technologies, information and electronic device technologies in particular.