****NON-TECHNICAL ABSTRACT**** In many materials with potentially great technological importance, such as high temperature superconductors, the electrically conducting state is created by chemically doping an otherwise insulating material. Therefore by varying a parameter, one is able to change a material from one that conducts electricity to one that does not (an insulator) and vice versa. Understanding the nature of this conductor-insulator transition represents an important issue for materials science and technology. It also presents a fundamental problem in condensed matter physics. Furthermore, many studies have shown striking similarities in the behavior of systems close to a conductor-insulator transition and those of various glassy materials, the understanding of which also presents one of the deepest and most interesting problems in physics. Glassy behavior is exhibited by many different types of materials, including window glasses, metals doped with magnetic impurities, polymers, gels, etc., all of which have a wide range of current and potential applications. This award supports a project that will address the problem of complex, glassy behavior near the conductor-insulator transition by performing electrical transport and noise measurements on semiconductor devices and high temperature superconductor materials. The anticipated results are expected to provide a fundamental insight into these problems, and may be of relevance for future applications. The project will give graduate and undergraduate students an excellent preparation for careers in academia, industry, and government.
This award supports a project that will tackle two of the grand scientific challenges in condensed matter physics: i) How do complex phenomena emerge from simple ingredients? and ii) What happens far from equilibrium and why? In particular, many strongly correlated electronic materials exhibit complex, inhomogeneous behavior near the transition from an insulating into a conducting state. The out-of-equilibrium dynamics may very well be the smoking gun manifestation of this emerging complexity. This project will address the problem of complexity near the conductor-insulator transition by carrying out a comprehensive, comparative study of charge dynamics in two types of materials: two-dimensional systems in semiconductor heterostructures and lightly doped cuprates. The experiments will involve transport combined with low-frequency dynamical response measurements. The carefully designed comparative study will make it possible to separate out the more universal behavior from the material specific one, and thus identify the main ingredients necessary for the development of successful theoretical models. This project will support the education and training of graduate and undergraduate students, who will acquire valuable technical and analytical skills for a wide range of careers in the areas of science and technology in academic, industrial or government settings. The PI and graduate students will also engage in a variety of outreach activities, such as the Annual Open House at the National High Magnetic Field Laboratory.
