Non Fermi Liquid Physics and Quantum Critical Phenomena

技术概述：该奖项支持凝聚态物理的理论和计算研究和教育。该研究旨在发展和验证理解不服从朗道-费米液体范式的材料的物理学所需的概念、理论和计算方法。该项目有4个主要组成部分：(1)PI计划对模型系统属性进行分析和数值计算，旨在解释和理解一种新型实验测量的含义；即“红外/光学霍尔效应”，它探测暴露在静态磁场和以红外或光学频率交替的电场中的电子的运动。(2)该组件侧重于“量子临界性”，即当材料的基态从一个相（例如顺磁性金属）变化到另一个相（例如反铁磁性金属）时发生的行为。接近量子临界点的材料通常表现出振幅大、范围长、变化缓慢的波动，这些波动根据经验已知与电子耦合，导致与费米液体理论的预测有很大的偏差。此外，这些波动的缓慢时空变化意味着它们的影响可以用量子场论的既定技术来研究。将进行分析计算，并与最近对准二维量子反铁磁跃迁的测量结果进行比较，并将其应用于高温超导。(3)这部分涉及开发和验证新的数值方法，用于计算传统方法无法充分描述的系统的热力学和动力学。近年来，基于“动态平均场”的近似方法取得了相当大的进展。求解动力学平均场方程的新方法已经发展起来，并将进一步改进，将在广泛的系统中实现和应用。(4) PI旨在将我们对平衡物理的理解扩展到非平衡领域，例如分子器件的纳米科学。新的解析和数值方法将探索计算系统在稳态非平衡状态的性质。这个研究项目将有助于培养能够从广阔的角度看待问题的青年科学家；将基本见解与具体应用相结合。非技术总结：该奖项支持凝聚态物理的理论和计算研究和教育。为什么整体大于部分之和？简单的组成部分，电子和原子是如何构成我们周围世界的基石，它们是如何结合在一起形成我们所看到的各种各样的事物的呢？本研究项目涉及的理论工作旨在解决这些问题，在材料理论的一个特定领域，即“非费米液体”金属的物理。“费米液体理论”是由苏联物理学家朗道（L. D. Landau）在20世纪50年代末创立的，是理解金属中电子性质的主流理论范式，并取得了广泛成功。然而，它明显未能描述例如氧化铜高温超导体材料在前所未有的高温下携带无电阻超电流的能力，锰氧化物化合物中电阻对磁场的“巨大”依赖，或者纳米级和“单分子”器件的电导特性的变化。更多例子的实验发现似乎指日可待。这项研究将有助于创造新的概念和新的理论，以及新的计算算法，这将使人们能够理解具有不同寻常性质的复杂材料，这是发现新现象和创造新技术的燃料。该研究项目将有助于培养能够从广阔的角度看待问题，将基本见解与具体应用相结合的青年科学家，以应对未来的科学和技术挑战。

TECHNICAL SUMMARY:This award supports theoretical and computational research and education in condensed matter physics. The research is aimed at developing and validating the concepts and the theoretical and computational methods needed to understand the physics of materials that do not obey the Landau Fermi liquid paradigm. There are 4 major components to the project: (1) The PI plans to carry out analytical and numerical calculations of model systems properties aimed at interpreting and understanding the implications of a new kind of experimental measurement; namely the "infrared/optical Hall effect," which probes the motion of electrons exposed to a static magnetic field and to an electric field alternating at infrared or optical frequencies. (2) This component focuses on "quantum criticality", the behavior occurring when the ground state of a material changes from one phase, for example paramagnetic metal, to another phase, for example antiferromagnetic metal. Materials near a quantum critical point typically exhibit large amplitude, long range, slowly changing fluctuations, which are known empirically to couple to the electrons, leading to large deviations from the predictions of fermi liquid theory. Moreover, the slow spatial and temporal variation of these fluctuations means that their effects can be studied using established techniques of quantum field theory. Analytical calculations will be performed, and compared to recent measurements on quasi two dimensional quantum antiferromagnetic transitions, with applications to high temperature superconductivity. (3) This component involves developing and validating new numerical methods for calculating the thermodynamics and dynamics of systems not adequately described by conventional methods. Considerable progress has been made in recent years based on the "dynamical mean field" approximation. New methods of solving the dynamical mean field equations have been developed and will be further improved, will be implemented for a wide range of systems, and applied. (4) The PI aims to extend our understanding of equilibrium physics into the nonequilibrium domain relevant for example for the nanoscience of molecular devices. New analytical and numerical methods will be explored for calculating the properties of systems in a steady state non-equilbrium situation.This research project will contribute to the training of young scientists who can look at problems from a broad perspective; combining fundamental insights with concrete applications.NON-TECHNICAL SUMMARY:This award supports theoretical and computational research and education in condensed matter physics. Why is the whole greater than the sum of its parts? How do simple constituents, the electrons and atoms which are the building blocks of the world around us, combine together to give amazing variety of things we see? This research project involves theoretical work designed to address these questions in one specific area of materials theory, namely the physics of "non-fermi-liquid" metals. "Fermi liquid theory", created by the Soviet physicist L. D. Landau in the late 1950s, is the reigning and widely successful intellectual paradigm for understanding the properties of electrons in metals. However, it fails conspicuously to describe for example the ability of the copper-oxide high temperature superconductor materials to carry a super-current with no electrical resistance at unprecedentedly high temperatures, the 'colossal' dependence of electrical resistance on magnetic field in manganese oxide compounds, or the changes to the conductance properties of nanoscale and "single molecule" devices. The experimental discovery of additional examples seems just around the corner. This research will contribute to the creation of new concepts and new theories, and new computational algorithms that will enable the understanding of complex materials with unusual properties that are the fuel for the discovery of new phenome and for the creation of new technologies. This research project will contribute to the training of young scientists who can look at problems from a broad perspective, combining fundamental insights with concrete applications, to tackle the future challenges of science and technology.