Bad Metal Behavior and the Metal-Insulator Transition

Florida State University, Tallahassee FL

Investigators

Abstract

NONTECHNICAL SUMMARY This 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 SUMMARY This 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.