NMR Investigations of Spin Density Waves in Organic Metals and Vortices in Superconductors

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w:\awards\awards96\num.doc 9705369 Clark This experimental research project employs techniques of nuclear magnetic resonance in study of the thermal and driven motions of the local broken symmetry ground state structures in CDW and SDW one-dimensional systems, and the motion of vortex structure in several Type-II superconductors. Organic metal systems for study include a Bechgaard salt alloy system and the blue bronze. Most of the experiments will employ pulsed NMR over a very wide range of frequencies and up to high pressures. In superconductors, recent NMR spin-echo field-rocking measurements will be extended to anisotropic superconductors to measure the anisotropy of the penetration depth; and to high field to measure the coherence length. Work is planned to extend the recent observations by NMR of rf-assisted flux-lattice annealing in anisotropic Type- II superconductors. Some very high magnetic field work will be performed at the National High Magnetic Field Laboratory. This study of unusual ground states in novel materials will extend the knowledge base and has potential to generate significant advances in basic solid state physics. It also will demonstrate new methods for using NMR which may be applicable in other circumstances. %%% This experimental research project uses primarily the technique of Nuclear Magnetic Resonance (NMR) to probe basic electrical properties of novel organic metal conductors, as well as aspects of the magnetic behavior in highly anisotropic superconductors. The organic conductors of interest exhibit nearly one-dimensional electrical conduction. Their electrical conduction is believed to occur by a novel mechanism known as a "sliding charge density wave", which involves a highly correlated motion of carriers, unlike conventional metals. The properties of this unusual effect, and materials that can exhibit it, a re of interest. Results from this research may include unusual new effects or materials which may find new application in technology. A portion of the work will be carried out at the National High Magnetic Field Laboratory. This research project is interdisciplinary in nature and involves both graduate and postgraduate students who will be excellently trained to enter positions in industry, government or education. ***