Disorder and the emergence of inhomogeneous phases in strongly correlated electron systems

该奖项支持与金属非均匀竞争秩序问题相关的理论和计算研究以及教育活动。越来越多的新材料表现出涌现的非均匀相，这是基态被调制的物质状态，可以显示各种类型的远程秩序。这种状态的理论，从根本上背离了凝聚态物理的基本动量-空间单粒子范式，仍然处于起步阶段。沿着这个方向，PI将研究非均匀秩序是如何出现的，以及系统如何根据无序、相互作用及其电子结构做出特定选择的一般问题。将研究适用于各种相互作用系统的模型，适用于重费米子、铁镍、铜和其他氧化物材料。更好地理解无序在竞争有序态中所起的作用，将有助于识别各种系统中最重要的不稳定性，并使研究人员能够关注诸如高温超导等外来有序现象的内在方面。该奖项支持研究，最终有望对应用氧化物材料的设计和开发产生影响。值得注意的是，目前整个电子工业都是建立在掺杂半导体器件的基础上的，可以说，它之所以如此成功，部分原因是找到了防止电子迁移受到掺杂过程中伴随的无序限制的解决方案。由于在相关系统中，特别是在新型氧化物中，杂质具有更重要的影响，特别是通过它们的非均相成核，这些问题代表了氧化物电子学在市场上取得成功之前需要克服的重要和实际障碍。PI将在项目过程中培养两名研究生。PI还将参与外展活动，教育盖恩斯维尔地区的学童关于超导性和有序与无序的概念，这些在许多科学学科中都很重要。该奖项支持与金属“非均匀竞争秩序”问题相关的理论和计算研究以及教育活动。当一种复杂的材料接近于从一个电子相过渡到另一个电子相时，两种或更多不同的量子力学态在能量上变得如此接近，以至于基本上无法区分时，就会出现这种迷人的情况。在存在少量杂质或缺陷的情况下，材料有时会形成一种不均匀的状态，而不是决定在这些状态中形成一种或另一种状态，这种状态在空间中每个点的组成都不同。表现出这种奇异行为的材料可能会被用于所谓的智能材料，这种智能材料可以改善许多不同电子设备的工作方式。在这个项目中，PI将对各种已知无序在其中发挥作用的新材料进行理论计算和计算机模拟，以了解超导性（一种可以无电阻导电的电子状态）和磁性如何受到杂质的影响。这是一项基础研究，旨在促进我们对杂质和缺陷非常敏感的材料的理解，这些材料会导致电子的不寻常的量子力学状态。这些状态中的许多似乎都与超导性有关。这项研究有助于理解导致超导性的材料的关键特性。PI将在项目过程中培养两名研究生。P.I.还将参与外展活动，教育盖恩斯维尔地区的学童关于超导性和有序与无序的概念，这在许多科学学科中都很重要。

TECHNICAL SUMMARY This award supports theoretical and computational research and educational activities related to the problem of inhomogeneous competing order in metals. An increasing number of novel materials exhibit emergent inhomogeneous phases, which are states of matter where the ground state is modulated and may display various types of long-range order. The theory of such states, which represents a fundamental departure from the basic momentum-space one-particle paradigms of condensed matter physics, is still in its infancy. Along this direction, the PI will study the general question of how inhomogeneous order emerges and how the particular choice taken by the system depends on disorder, interactions, and its electronic structure. Models will be studied which are applicable to a diverse class of interacting systems, appropriate for heavy fermion, iron-pnictide, cuprate, and other oxide materials. An improved understanding of the role of disorder in the presence of competing ordered states will facilitate the identification of the most important instabilities in various systems, and enable researchers to focus on the intrinsic aspects of exotic ordering phenomena such as high temperature superconductivity. This award supports research, which is ultimately expected to have an impact on the design and development of oxide materials for applications. It is noteworthy that the entire electronics industry is built on doped semiconductor devices at present, and may be said to have been so successful in part because solutions were found to prevent electron mobilities from being limited by disorder which accompanies the doping process. Since in correlated systems and novel oxides in particular, impurities have a much more important impact, specifically through their nucleation of inhomogeneous phases, these problems represent important and also practical hurdles to be surmounted before oxide electronics can succeed in the marketplace. The PI will train two graduate students during the course of the project. The PI will also engage in outreach activities to educate school children in the Gainesville area about superconductivity and notions of order and disorder which are important in many disciplines of science. NONTECHNICAL SUMMARY This award supports theoretical and computational research and educational activities related to the problem of "inhomogeneous competing order" in metals. This fascinating situation occurs when a complex material is close to making a transition from one electronic phase to another, and two or more different quantum mechanical states become so close in energy as to be essentially indistinguishable. Rather than deciding to form in one or the other of these states, in the presence of small amounts of impurities or imperfections, the material sometimes forms an inhomogeneous state, which varies in composition from point to point in space. Materials that exhibit such exotic behavior can be potentially tuned for use in so-called smart materials which can improve the way many different electronic devices work. In this project, the PI will perform theoretical calculations and computer simulations on a variety of novel materials where disorder is known to play a role of this type, to understand how superconductivity, an electronic state that can conduct electricity without resistance, and magnetism can be influenced by impurities. This is fundamental research aimed to advance our understanding of materials that are very sensitive to impurities and imperfections leading to unusual quantum mechanical states of electrons. Many of these states appear to be connected to superconductivity. This research contributes to understanding key properties of materials that lead to superconductivity.The PI will train two graduate students during the course of the project. The P.I. will also engage in outreach activities to educate schoolchildren in the Gainesville area about superconductivity and notions of order and disorder which are important in many disciplines of science.