Emergent Properties of Highly Correlated Electronic Systems

该奖项支持对高度相关电子系统的紧急特性的研究和教育。这里进行的研究的主要重点是在理论上表征相互作用的电子（即新的物质状态）的定性新行为，以及新的参数制度，其中熟悉的物质状态以新的和不同的方式表现。此外，部分研究还定性地探索了电子之间的微观相互作用与控制固体宏观行为的有效参数之间的关系。PI在“电子液晶”理论中对新物质状态的探索继续进行。这项工作是基于经典液晶和强相互作用电子的相应相之间的类比。 电子液晶是一种量子态，其行为介于费米液体和维格纳晶体之间。这些状态的例子最近已经被实验观察到：在高迁移率量子霍尔器件中看到的各向异性态（量子霍尔向列相）和最近在Sr3Ru2O7中发现的变磁超导相。需要解决的更微观的问题涉及超导Tc的物理。理论上解决了一些问题。 为什么超导性的转变温度通常如此之低，而其他有序，如铁磁性，却常常在更高的温度下开始？为什么在铜氧化物高温超导体中，存在一个Tc最大的“最佳"掺杂？“过度掺杂”的铜酸盐中有什么过量？是否存在超导电性的最佳介观结构，即增强电子配对强度而不太强烈抑制超流体刚度的结构？该研究还试图解释铜氧化物中广泛存在的中尺度不均匀性证据的重要性。自组织（即条纹）和无序成核。这项研究的动机是需要澄清这些观察结果是复杂的细节还是对高温超导机制至关重要。所做的努力具有更广泛的科学和教育影响。在科学上，对高温超导起源的理解有影响，因为这开辟了新的理论机会，并提供了更好的能力来设计具有这种非常理想的特性的材料。 让学生和博士后研究人员参与各种 问题和理论技术的使用提供了一个特殊的培训，有才华的年轻人。过去的学生和博士后研究人员已经进入大学教师职位，并在教学和研究中有自己的职业生涯，有些人在高科技公司和主流物理学之外的各种其他领域找到了成功的职位。非技术性总结：该奖项支持对奇异性质和不寻常材料的无法解释的电子状态的研究和教育。在这里进行的研究的广泛的主旨是定性的新行为和新的物质状态的理论表征，以及调查如何熟悉的形式的物质可以表现在新的和不同的方式。这项研究通过观察电子的行为和构成材料的原子的微观水平来探索这些不寻常的物质状态，然后将这些行为与材料作为一个固体整体所看到的大尺度性质联系起来。寻找新的物质状态继续了PI在“电子液晶”理论中的持续努力。"这项工作发展了一些理论，解释为什么有些材料的电子不仅仅是静止地或多或少均匀分布，而是以各种模式聚集在一起。要解决的问题还涉及超导材料的物理学，这些材料可以无电阻导电，因此不会浪费能量。“这些问题都很基本。 是什么让超导体的工作温度如此之低？为什么在某些高温超导体中，存在一种工作温度最高的“最佳”成分？有没有最佳的方法来创造超导性的结构，提高性能的结构？这项研究的动机是需要澄清哪些实验观察是复杂的细节，哪些是发现解释高温超导所需机制的重要线索。所做的努力具有更广泛的科学和教育影响。在科学上，对高温超导起源的理解有影响，因为这开辟了新的理论机会，并提供了更好的能力来设计具有这种非常理想的特性的材料。 让学生和博士后研究人员参与各种 问题和理论技术的使用提供了一个特殊的培训，有才华的年轻人。过去的学生和博士后研究人员已经进入大学教师职位和他们自己的教学和研究职业生涯，有些人在高科技公司和主流物理学以外的各种其他领域找到了成功的职位。

TECHNICAL SUMMARY:This award supports research and education on emergent properties of highly correlated electronic systems. The main thrust of the research undertaken here is the effort at theoretical characterization of qualitatively new behaviors of interacting electrons (i.e. new states of matter) as well as new regimes of parameters in which familiar states of matter behave in new and different ways. In addition, some of the research explores qualitatively the relation between the microscopic interactions between electrons and the effective parameters that control the macroscopic behavior of solids.The search for new states of matter continues an ongoing effort by the PI in the theory of ''electronic liquid crystals.'' This work is based on an analogy between classical liquid crystals and corresponding phases of strongly interacting electrons. Electronic liquid crystals are quantum states with behaviors intermediate between a Fermi liquid and a Wigner crystal. Examples of such states have recently been observed experimentally: the anisotropic states (quantum Hall nematics) that are seen in high mobility quantum Hall devices and the metamagnetic nematic phase that has recently been identified in Sr3Ru2O7. The more microscopic issues to be addressed involve the physics of the superconducting Tc. A number of questions are addressed theoretically. What is it about superconductivity that causes transition temperatures, generally, to be so low, while other orders, such as ferromagnetism, frequently onset at much higher temperatures? Why is there, in the cuprate high temperature superconductors, an ''optimal'' doping at which Tc is maximal ? what is there an excess of in ''overdoped'' cuprates? Are there optimal mesoscale structures for superconductivity, structures that enhance the strength of the electron pairing without too strongly suppressing the superfluid stiffness? The research also seeks to interpret the importance of evidence of wide-spread mesoscale inhomogeneities in the cuprates ? both self-organized (i.e. stripes) and nucleated by disorder. The research is motivated by a need to clarify whether these observations are complicating details or essential to the mechanism of high temperature superconductivity.The effort undertaken has broader impacts with both scientific and educational consequences. Scientifically, there is impact in extending the understanding of the origins of high temperature superconductivity because that opens new theoretical opportunities as well as providing better ability to design materials with this highly desirable property. Involving students and postdoctoral researchers in the diverse problems and theoretical techniques used provides an exceptional training for talented young people. Past students and postdoctoral researchers have gone on to university faculty positions and their own careers in teaching and research and some have found successful positions in high tech companies and a variety of other fields outside of mainstream physics.NONTECHNICAL SUMMARY:This award supports research and education on exotic properties and unexplained electronic states of unusual materials. The broad thrust of the research undertaken here is the theoretical characterization of qualitatively new behaviors and new states of matter as well as investigating how familiar forms matter can be made to behave in new and different ways. This research explores these unusual states of matter by looking at the behavior of electrons and the microscopic level of the atoms that make up the material and then connecting those behaviors with the large scale properties which are seen in the material as a solid whole.The search for new states of matter continues an ongoing effort by the PI in the theory of ''electronic liquid crystals.'' This work develops theories of why some materials have electrons that are not just quiescently distributed more or less uniformly but which instead group together in various patterns.The issues to be addressed also involve the physics of the superconducting materials, those which can conduct electricity with no resistance and thus no waste of energy. The questions are quite basic. What is it about superconductivity that causes working temperatures, generally, to be so low? Why is there, in some high temperature superconductors, an ''optimal'' composition at which the working temperature is highest? Are there optimal ways of creating structures for superconductivity, structures that enhance performance? The research is motivated by a need to clarify which experimental observations are complicating details and which are essential clue to discovering to the mechanism needed to explain high temperature superconductivity.The effort undertaken has broader impacts with both scientific and educational consequences. Scientifically, there is impact in extending the understanding of the origins of high temperature superconductivity because that opens new theoretical opportunities as well as providing better ability to design materials with this highly desirable property. Involving students and postdoctoral researchers in the diverse problems and theoretical techniques used provides an exceptional training for talented young people. Past students and postdoctoral researchers have gone on to university faculty positions and their own careers in teaching and research and some have found successful positions in high tech companies and a variety of other fields outside of mainstream physics.