Renormalized Insulators: On the Verge of Magnetism

重正化绝缘体：处于磁性的边缘

• 批准号: 1206763
• 负责人: John DiTusa
• 金额: $ 37万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206763&HistoricalAwards=false
• 关键词: Renormalized; Insulators; Verge; Magnetism

****Technical Abstract****This project is designed to extend knowledge of strongly correlated electron systems into the regime of strongly interacting, or highly renormalized, insulators on the verge of magnetism. Previous investigations by the PI and collaborators have indicated that this is a very rich vein of research because of the importance of both semiconductor physics and magnetism. The competing interactions inherent in these carefully characterized chemically substituted small band-gap insulators often lead to quantum phase transitions in the presence of strong correlations and disorder. Typical systems that will be investigated include iron-based non-magnetic insulators, such as FeSi, FeS2, and related materials, where a transition from a strongly correlated-insulator-to-magnetic metal transition can be accessed by doping. The goals are to discover what novel phenomena exist when carriers are doped into these strongly correlated insulators placing them in the unique regime where low carrier density, disorder, magnetism, and, in some cases, finite size are all important aspects. In addition we will be exploring the nucleation, imaging, and control of the magnetic Skyrmion phases that have recently been discovered in the mono-silicide and -germanide materials having the FeSi crystal structure in thin films of these materials. Students on many levels, as well as high school teachers will explore these materials searching for novel transport, magnetic, thermodynamic, and optical properties that may be exploited in future technologies.****Non-Technical Abstract****In order to accelerate the technological revolution that has placed high speed computation and information storage at our fingertips almost anywhere on Earth, new ideas are essential. One pathway for progress in semiconductor device design, known as spintronics, seeks to make use of the magnetic degrees of freedom to the same extent that charge degrees of freedom are used in present day silicon technologies. As scientists have sought to control or manipulate the electron spin, the intrinsic magnetic property of electrons, they have recognized the utility of materials that are both magnetic and semiconducting. This work seeks to extend our knowledge of magnetic semiconductors by investigating a series of compounds composed of transition metals and silicon or germanium where both semiconducting and magnetic behavior are known to emerge. The chemical flexibility that these systems offer while maintaining a common crystal structure allows enormous control over their physical properties making them ideal for discovering new behaviors at the intersection of semiconductor physics and magnetism. Also, the unusual symmetry of the underlying crystal structure of one family of these compounds has been shown to induce ~100 nm sized toroidal shaped magnetic structures, known as magnetic Skyrmions, for a range of temperatures and magnetic fields. This project investigates the necessary elements for nucleating, imaging, and controlling these novel magnetic structures both as a fundamental exploration and to assess their possible relevance for future technologies. Students on many levels, as well as high school teachers, will be exploring magnetic, electric, optical, and thermodynamic properties of these magnetic semiconductors in crystalline, thin film, and nanowire form.

****技术摘要****该项目旨在将强相关电子系统的知识扩展到强相互作用或高度重整化的磁性边缘绝缘体的体系中。PI和合作者先前的调查表明，由于半导体物理学和磁学的重要性，这是一个非常丰富的研究脉络。在这些经过仔细表征的化学取代的小带隙绝缘体中，固有的竞争相互作用经常导致在强相关性和无序存在下的量子相变。将研究的典型系统包括铁基非磁性绝缘体，如FeSi， FeS2和相关材料，其中可以通过掺杂获得从强相关绝缘体到磁性金属转变的过渡。目标是发现当载流子被掺杂到这些强相关绝缘体中时存在的新现象，将它们置于低载流子密度、无序、磁性以及在某些情况下有限尺寸都是重要方面的独特状态。此外，我们将探索最近在具有FeSi薄膜结构的单硅化物和-锗化物材料中发现的磁性Skyrmion相的成核、成像和控制。不同层次的学生以及高中教师将探索这些材料，寻找可能在未来技术中利用的新的输运、磁性、热力学和光学性质。****非技术摘要****为了加速技术革命，使高速计算和信息存储几乎在地球上的任何地方，我们的指尖，新的想法是必不可少的。半导体器件设计的一个进步途径，被称为自旋电子学，寻求利用磁性自由度达到与目前硅技术中使用的电荷自由度相同的程度。当科学家们试图控制或操纵电子自旋（电子固有的磁性）时，他们已经认识到磁性和半导体材料的实用性。这项工作旨在通过研究一系列由过渡金属和硅或锗组成的化合物来扩展我们对磁性半导体的认识，其中半导体和磁性行为已知会出现。这些系统在保持共同晶体结构的同时提供的化学灵活性允许对其物理特性进行巨大的控制，使其成为在半导体物理和磁性交叉点发现新行为的理想选择。此外，这些化合物的一个家族的潜在晶体结构的不寻常的对称性已经被证明可以在一定的温度和磁场范围内诱导出~ 100nm大小的环形磁性结构，称为磁性Skyrmions。该项目研究了成核、成像和控制这些新型磁性结构的必要元素，作为基础探索，并评估它们与未来技术的可能相关性。不同层次的学生，以及高中教师，将探索这些磁性半导体晶体、薄膜和纳米线形式的磁性、电学、光学和热力学性质。