Complex Behavior Near the Metal-Insulator Transition

Florida State University, Tallahassee FL

Investigators

Abstract

Intellectual Merit The metal-insulator transition (MIT) is one of the oldest, yet one of the fundamentally least understood problems in condensed matter physics. In the last few years, striking examples of complex ordering around the metal-insulator transition are starting to emerge, due to advances of both the experimental probes and the theoretical tools available. In many cases, fascinating new evidence reveals that genuinely new phenomena arise in presence of disorder and impurities. Put quite simply, a given configuration of impurities may locally favor one or another of several competing phases of matter. In many instances this gives rise to strongly inhomogeneous states that feature an enormous number of low-lying metastable configurations - producing qualitatively new excitations, slow relaxation, and glassy fluctuations and response. Even more surprisingly, recent work suggests that a plethora of intermediate heterogenous phases may emerge between the metal and the insulator, possibly even in absence of disorder. Such complexity emerges as a new paradigm of the metal-insulator transition region. These phenomena seem to dominate the observable properties in many physical systems, ranging from CMR manganites and high Tc cuprates, to two dimensional electron gases in MOSFETs, diluted magnetic semiconductors, and even the Kondo alloys. The topics that we plan to address in the next three years include: (1) Local quantum criticality at the Mott-Anderson transition; (2) Role of long ranged RKKY interaction and random singlet correlations within the electronic Griffiths phase in the MIT critical region; (3) How is the metal-insulator transition modified in systems featuring strongly inhomogeneous (cluster) magnetic or charge-ordered phases? (4) Self-organized electron glasses and the MIT in doped Mott insulators. Broader Impact Funding of the proposed work will allow the PI to integrate research at the forefront of condensed matter science in a world-class facility, and education at all academic levels: K-12, undergraduate, and graduate, through the following activities: (A) Outreach programs: The PI will continue to promote and enhance scientific and technological understanding and importance of our 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 bring the most recent discoveries within reach of the youngest. (2) The PI will act as a Judge at annual Regional Science Fairs, as he has been doing over the last five years. These Fairs involve K-12 students from public and private school within the region; (3) The PI will participate in the FSU Physics Department Open House (PDOP) activities. (4) The PI will participate in the NHMFL Annual Open House activities. (B) Research Experiences for Undergraduates (REU) program. A REU Site has been established at the NHMFL. It hosts a summer internship program for undergraduates who come from all over the US. The PI will provide an opportunity for interns to spend two summer months working on one of the research projects. (C) FSU graduate students will be trained. The PI will supervise the research of several graduate students in physics, who will be supported from the NSF grant. In order for these activities to be effective, the PI needs to obtain funding that will allow him to conduct research at the forefront of condensed matter science. ***