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CM Seminar: "Neutron scattering in 4 dimensions : from magnetic continua to isotropic oscillators"

Event Type
190 Engineering Sciences Bldg 
Feb 14, 2014   1:00 pm  
Dr. Steve Nagler, Oak Ridge National Laboratory, Neuron Scattering Science Division
Originating Calendar
Physics - Condensed Matter Seminar

Next generation of time-of-flight inelastic neutron scattering instruments are now enabling the exploration of new realms of dynamics in solids.  In this talk I will briefly describe spectrometers now operating at the Spallation Neutron Source, showing how updated experimental methods are enabling unprecedented investigations of excitations in materials.  I will then focus in more detail on one recent experiment where startling and beautiful results have been obtained.  In the course of investigating magnetic excitations in the strongly correlated uranium based material uranium nitride (UN)  an unexpected a ladder of equally spaced well-defined modes was observed extending to energies at least as high as 500 meV.  Analysis of the momentum and energy dependence of the scattering and additional insights obtained from ab-initio calculations show that each individual nitrogen atom is a nearly ideal text-book realization of the isotropic three dimensional quantum harmonic oscillator, one of the few exactly solvable problems in quantum mechanics.  This behavior arises in part because of the large mass difference between the nitrogen and uranium atoms.  The phenomenon has now been observed in several other binary materials with asymmetric masses.  For more information see Nature Communications 3, 1124 (2012); also research highlights comment in Nature Materials 11, 1002 (2012).

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