Charge-Density Waves: Novel X-ray Scattering Studies

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This individual investigator award will provide funds for a project to measure the dynamic atomic-scale structure of charge-density waves driven by an applied electric field over randomly located impurity atoms. Charge density wave systems are a good example of a driven periodic system in the presence of disorder. To perform quantitative tests of some novel theories for such systems, several important quantities need to be measured. These include measurements of the steady-state (equilibrium) dynamics and measurements of the coupling between the electronic and the lattice degrees of freedom. This project will (a) continue to develop X-ray Photon Correlation Spectroscopy (at the Advanced Photon Source) for measurements of the equilibrium dynamics and will (b) assess (at CHESS) the feasibility of using resonant-elastic-scattering to separate the response of the electrons from the response of the crystal lattice. The potential impact of these measurements is large as the results relate directly to a diverse array of systems including: magnetic-bubble lattices driven by a magnetic-field, Wigner crystals, colloidal suspensions driven by an electric field, driven arrays of Josephson-junctions, and the growth of crystals on substrates. The impact of this project on advancing education and human resources development includes continuing the research group's demonstrated practice of pro-actively searching out, recruiting and supporting women and under-represented minorities at the undergraduate, graduate, and postdoctoral levels.X-ray diffraction has historically been the technique of choice for measuring the structure of matter on atomic length scales. The continuing development of time-resolved x-ray techniques allows the atomic positions to be determined on ever-faster time scales during chemical, physical, and biological processes. Time-resolved x-ray measurements span length-scales from atomic to macroscopic distances and time-scales from 1 millionth to 1000 seconds. This individual investigator project will develop new x-ray techniques for studying a variety of problems in condensed-matter physics. X-ray technique development will occur in the process of studying of charge-density waves found in the quasi one-dimensional metal NbSe3. This system is known to be a nearly ideal realization of a physical system with a large number of internal degrees of freedom that can be driven over disorder, thus it forms an. excellent one which to use new improved techniques. This project will (a) continue to develop X-ray Photon Correlation Spectroscopy (at the Advanced Photon Source) for measurements of the equilibrium dynamics and will (b) assess (at CHESS) the feasibility of using resonant-elastic-scattering to separate the response of the electrons from the response of the crystal lattice. The potential impact of these measurements is large as the results relate directly to a diverse array of other systems, some of which have the potential for technological applications.. The impact of this project on advancing education and human resources development includes continuing the research group's demonstrated practice of pro-actively searching out, recruiting and supporting women and under-represented minorities at the undergraduate, graduate, and postdoctoral levels.