Bad Metal Behavior and the Metal-Insulator Transition

该奖项支持在典型金属和绝缘体之间表现出某些特性的材料的理论和计算研究和教育。这些奇怪的“坏”金属具有惊人的高电阻和不寻常的热性能。对于处于这个范围内的材料，材料中电子的动力学发生了巨大的变化：它们变慢了，这反过来又产生了电子在穿过固体的过程中所探索的势能景观的所有关键特征的基本修改。长期以来，这种机制究竟发生了什么一直是一个基本的科学难题；现在，由于最近的进展，新的见解近在眼前。在过去的几年里，更现实的微观建模和新的实验能力为这个项目提供了令人兴奋的新研究机会，以了解这些材料行为的基本方面。该项目还将包括对理论和计算凝聚态物理研究生的培训。科学促进会继续透过各种外展活动，向公众推广和加强广泛的科技认识，以及基础研究的重要性。这将包括：1)在小学举办讲座，以普及科学技术，并使年轻学生能够接触到最新的科学发现；2)担任年度区域科学博览会评委，参与区域内公立和私立学校的K-12学生；3)作为“佛罗里达青年学者”计划的一部分，与高中暑期实习生合作，使他们能够通过开发JAVA动画和其他基于网络的材料，将前沿科学带给广大公众。该奖项支持介于金属和绝缘体之间的材料的理论和计算研究和教育。这种所谓的“坏金属”状态介于金属和绝缘体之间，其典型特征是其性质与任何一相都不同。PI将从理论上研究金属-绝缘体跃迁（MIT）区域的几个基本方面，这些方面由于最近的实验发现而受到关注，这将由于新一代的理论工具而成为可能：1)将为半导体表面上的新型离子系统开发第一原理建模，允许通过纳米级控制和成像探索掺杂半导体中的MIT。2)通过快速过冷获得的物质亚稳相将被探索，这些亚稳相通常显示出无定形或非常规的电子秩序周期形式。3)电子-电子和电子-声子相互作用的显著增加作用将在通过无序驱动的MITs调整的系统中进行研究，解决长期存在的Mooij相关性和相关电阻率饱和度的难题。该项目还将包括对理论和计算凝聚态物理研究生的培训。科学促进会继续透过各种外展活动，向公众推广和加强广泛的科技认识，以及基础研究的重要性。这将包括：1)在小学举办讲座，以普及科学技术，并使年轻学生能够接触到最新的科学发现；2)担任年度区域科学博览会评委，参与区域内公立和私立学校的K-12学生；3)作为“佛罗里达青年学者”计划的一部分，与高中暑期实习生合作，使他们能够通过开发JAVA动画和其他基于网络的材料，将前沿科学带给广大公众。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education on materials that exhibit properties that fall somewhere between those of typical metals and insulators. These curious "bad" metals have surprisingly high resistance and unusual thermal properties. For materials that fall within this regime, the dynamics of electrons in the material change dramatically: they slow down, and this in turn produces essential modifications of all key features of the potential energy landscape that an electron explores on its way through the solid. What precisely happens in this regime has long presented a basic science puzzle; now, due to recent progress, new insight is at hand. More realistic microscopic modeling and new experimental capabilities that have occurred in the last few years are opening exciting new research opportunities that are exploited in this project to understand fundamental aspects of the behavior of these materials.This project will also involve training of graduate students in theoretical and computational condensed matter physics. The PI will continue to promote and enhance broad scientific and technological understanding and the importance of fundamental research to the general public through various outreach activities. These will include: 1) Presenting lectures at elementary schools in order to popularize science and technology and to bring recent scientific discoveries within reach of young students; 2) Serving as a judge at annual regional Science Fairs that involve K-12 students from public and private schools within the region; 3) Working with high-school summer interns as a part of the "Florida Young Scholar" program, enabling them to bring cutting-edge science to the public at large through the development of JAVA animations and other web-based materials.TECHNICAL SUMMARYThis award supports theoretical and computational research and education on materials that fall somewhere between metals and insulators. This so-called "bad metal" regime between a metal and an insulator is typically characterized by behavior that is qualitatively different from either phase. The PI will theoretically examine several fundamental aspects of the metal-insulator transition (MIT) region that have come into focus due to very recent experimental discoveries, which will be possible thanks to a newer generation of theoretical tools: 1) First-principles modeling will be developed for novel ionic systems on semiconductor surfaces, allowing to explore the MIT in doped semiconductors with nanoscale control and imaging. 2) Metastable phases of matter that are obtained by rapid supercooling will be explored, which often display amorphous or unconventional periodic forms of electronic order. 3) The dramatically increased role of electron-electron and electron-phonon interactions will be investigated in systems tuned through disorder-driven MITs, addressing the long-standing puzzles of Mooij correlations and the related resistivity saturation.This project will also involve training of graduate students in theoretical and computational condensed matter physics. The PI will continue to promote and enhance broad scientific and technological understanding and the importance of fundamental research to the general public through various outreach activities. These will include: 1) Presenting lectures at elementary schools in order to popularize science and technology and to bring recent scientific discoveries within reach of young students; 2) Serving as a judge at annual regional Science Fairs that involve K-12 students from public and private schools within the region; 3) Working with high-school summer interns as a part of the "Florida Young Scholar" program, enabling them to bring cutting-edge science to the public at large through the development of JAVA animations and other web-based materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.