Quantum Critical Phenomena and Non Fermi Liquid Physics

该奖项支持理论研究和教育，以阐明控制表现出新型电子秩序（如超导和磁性形式）的材料行为的原理，开发可靠计算这些特性所需的方法，并应用这些知识来设计和控制具有所需特性的材料。研究的一个重点是进一步发展和更广泛地应用最近提出的新的计算方法。这些“连续时间量子蒙特卡罗”方法为定量研究开辟了大量以前难以解决的问题。PI将进一步改进这些方法，并利用它们来了解高温超导体和其他超出标准朗道-费米液体概念的材料的性质。研究的另一个主题是关于被电流、电压或高强度光激发而失去平衡的材料的特性。发展非平衡域的一般理论提出了基本的智力挑战，对于理解纳米级器件的特性至关重要，并对太阳能发电产生影响。PI还旨在促进对量子临界性的理解。接近量子临界点的物质通常表现出振幅大、范围长、变化缓慢的波动，导致与朗道-费米液体理论的预测有很大的偏差。该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。PI积极组织并在暑期学校授课，在那里凝聚态理论产生的思想被带到更广泛的科学家面前。该奖项支持理论研究和教育，以阐明基本问题，如：电子和原子，构成我们周围世界的简单成分，是如何结合在一起产生在天然材料中发现的惊人的各种行为的？我们如何理解这些现象并控制它们来生产新设备和新技术？PI将进一步开发新的先进计算工具，并使用它们来研究高温超导体材料的模型，这些材料在金属状态下表现出不同寻常的电子特性，随着温度的降低，这些特性会让位于奇特的超导形式。这些材料的金属态不符合低温下金属中电子的标准模型。在超导状态下，电子以这样一种方式组织起来，它们可以导电而不耗散。和金属态一样，高温超导体中的超导性也是不寻常的。PI将探索在绝对零度下发生的量子相变是否与高温超导体的不寻常特征密切相关。量子相变涉及到由海森堡不确定性原理的量子力学波动驱动的物质从一种状态到另一种状态的转变，与热波动相反，热波动驱动更熟悉的相变，如水到蒸汽。PI还将促进我们对许多相互作用的粒子的系统的理解，这些粒子远离平衡的平衡，就像在原子或分子的小结构中施加电压时可能发生的那样。这项研究可能会对各个学科产生影响，包括凝聚态物理、材料科学和电气工程领域。它为纳米尺度（原子和分子的尺度）可能的新设备技术奠定了基础。该项目还有助于培训年轻科学家，使他们能够将基本见解与具体应用相结合。PI积极组织并在暑期学校授课，在那里凝聚态理论产生的思想被带到更广泛的科学家面前。

TECHNICAL SUMMARYThis award supports theoretical research and education to elucidate the principles governing the behavior of materials exhibiting novel electronic orders such as forms of superconductivity and magnetism, to develop the methods needed to reliably calculate these properties, and to apply the knowledge to design and control materials with desired properties.A focus of the research is to further develop and more widely apply new computational methods which have been recently introduced. These "continuous time quantum Monte Carlo" methods have opened up wide classes of previously intractable problems to quantitative investigation. The PI will further improve the methods and use them to gain understanding of the properties of high temperature superconductors and other materials with properties that are beyond those of the standard Landau-Fermi liquid concept. Another theme of the research concerns the properties of materials driven out of equilibrium by a current, voltage, or high intensity optical excitation. Developing a general theory of the nonequilibrium domain raises fundamental intellectual challenges, is essential for understanding the properties of nanoscale devices and has impact on solar energy generation. The PI also aims to advance understanding of quantum criticality. Materials near a quantum critical point typically exhibit large amplitude, long range, slowly changing fluctuations, leading to large deviations from the predictions of Landau-Fermi liquid theory.This project will contribute to the training of young scientists who can look at problems from a broad perspective, combining fundamental insights with concrete applications. The PI is active in organizing and lecturing at summer schools where the ideas generated in condensed matter theory are brought to a wider range of scientists.NONTECHNICAL SUMMARYThis award supports theoretical research and education to illuminate fundamental questions such as: How do electrons and atoms, the simple constituents which make up the world around us, combine to produce the astounding variety of behavior found in natural materials? How do we understand these phenomena and control them to produce new kinds of devices and new technologies? The PI will further develop new advanced computational tools and use them to study models of high temperature superconductor materials that exhibit unusual electronic properties in the metallic state that give way to exotic forms of superconductivity as the temperature is lowered. The metallic state of these materials does not conform to the standard model for electrons in metals at low temperatures. In a superconducting state, electrons organize themselves in such way that they can conduct electricity without dissipation. Like the metallic state, superconductivity in high temperature superconductors is also unusual. The PI will explore whether close proximity to a quantum phase transition which occurs at the absolute zero of temperature might be responsible for the unusual features of high temperature superconductors. A quantum phase transition involves the transformation from one state of matter to another driven by the quantum mechanical fluctuations of Heisenberg's uncertainty principle, as opposed to thermal fluctuations which drive more familiar phase transformations like water to steam. The PI will also advance our understanding of systems of many interacting particles that are driven far from the balance of equilibrium, as might occur from a voltage applied to the electrons in small structure of atoms or molecules.The research may have impact across disciplines, including the fields of condensed matter physics, materials science, and electrical engineering. It contributes to the foundations of possible new device technologies at the nanoscale - the scale of atoms and molecules.This project also contributes to the training of young scientists to enable them to combine fundamental insights with concrete applications. The PI is active in organizing and lecturing at summer schools where the ideas generated in condensed matter theory are brought to a wider range of scientists.