Dynamic Correlations in Strongly Fluctuating Condensed Matter

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Strongly fluctuating solids are interesting because their properties are anomalous, potentially useful, and difficult to predict. Based on inelastic neutron scattering, this experimental project will providedetailed information about dynamic correlations in such materials leading to progress in understanding and predicting their cooperative behavior. The materials to be studied are (i) Well-defined model systemslinked to recent developments in condensed matter theory. Examples include spin ladders with a field induced quantum phase transition and an extended high field quantum critical phase. (ii) Magnetic materialsdisplaying unusual phenomena that cannot be described satisfactorily with existing theories. Examples include oxides and organic materials where exchange interactions do not favor static long range spin order.(iii) Materials where fluctuations affect possibilities for future technological applications. Examples include assemblies of ferro-magnetic nano-wires where transverse standing spin waves and inter-wire correlations will be probed. The scientific projects will be the basis for an educational program for students and post doctoral fellows. They will learn to apply innovative neutron scattering technique to modern problems in condensed matter physics thus preparing them to be major scientific contributors to the spallation neutronsource. Many applications of materials rely on or are severely affected by random atomic scale motion called fluctuations. This is increasingly true in nano-technology where device dimensions are reduced towards theatomic spacing. Materials properties linked to fluctuations are at present difficult to predict. Therefore experiments such as those proposed here are the key to progress. To probe motion on the atomic scale the project will use the powerful inelastic neutron scattering technique. Careful analysis of the pattern of neutron scattering from a sample reveals detailed information about spatial and temporal correlations between the atoms that make up the solid. Prototypical magnetic materials that are strongly affected by fluctuations will be the focus of the experiments. These include so-called spin-ladders where quantum fluctuations can be tuned through the application of a strong magnetic field, frustrated magnetic systems that fail to order due to competing interactions, and ferro-magnetic nano-wires with anomalous spin wave propagation. Education will be an integral part of the project where students and post doctoral fellows will carry out experiments using cutting edge instrumentation and analysis under the guidance of the principal investigator. The goal is to educate creative experimental physicists with expertise in the application of neutron scattering to materials science. This is crucial as the nation invests $1.4B in the worlds most advanced neutron scattering facility at Oak Ridge National Laboratory.