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Glyde-neutron-scattering-highlights

Excitations and Bose-Einstein Condensation in Quantum Liquids in Disorder Henry R. Glyde, University of Delaware, DMR-9972011.

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Glyde-neutron-scattering-highlights

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  1. Excitations and Bose-Einstein Condensation in Quantum Liquids in DisorderHenry R. Glyde, University of Delaware, DMR-9972011 Neutron scattering measurements of the elementary excitations and of Bose-Einstein condensation (BEC) in quantum liquids confined in porous media reveal a possible “mixed” quantum state in disorder. In this “mixed” state there is evidence for BEC but there is no superfluidity. Measurements are made at the Institut Laue Langevin, Grenoble, France and at the ISIS Facility, Rutherford Appleton Laboratory, UK. Liquid 4He confined in porous media is an example of “Bosons” in “disorder.” Other examples are Cooper pairs in High Tc materials, flux lines in High Tc materials and Josephson Junction Arrays. We find that the characteristic phonon-roton excitations of superfluid 4He are remarkably little modified by disorder. However, new excitations propagating in the liquid layers near the porous media surfaces appear. These new excitations can be related to thermodynamic properties in disorder. Most interestingly, our data shows evidence for “localized” BEC, or a “Bose glass” state, in disorder at temperatures immediately above the superfluid phase where there is BEC but no macroscopic superflow. Figure 1. Top: The Insitiut Laue Langevin (just behind the ESRF synchrotron ring) in Grenoble. Bottom: Left to right, Jacques Bossy, Henry Glyde, Francesco Albergamo and Olivier Plantevin in front of the IN6 neutron spectrometer of ILL.

  2. Excitations and Bose-Einstein Condensation in Quantum Liquids in DisorderHenry R. Glyde, University of Delaware, DMR-9972011 An educational goal is to train young scientists in neutron scattering techniques in preparation for the new Spallation Neutron Source (SNS) now under construction at Oak Ridge National Laboratory (ORNL). Associated with this research are: Graduate Students: F. Albergamo - (PhD U. Paris), now a post-doc at ILL/Delaware J. L. Dubois - PhD Delaware, summer 2002 A. R. Sakhel - PhD Delaware, summer 2003 Post-doctoral Associates: R. T. Azuah - now instrument scientist at NIST Center for Neutron Research, Gaithersburg, MD O. Plantevin - now instrument scientist at ESRF, Grenoble Collaborators: B. Fåk - ISIS Facility, Rutherford Appleton Lab, UK J. Bossy - CNRS/ILL, Grenoble, France W. G. Stirling - ESRF, Grenoble Figure 2. Discussing analsis of neutron scattering data at Delaware are (left to right): Zhicheng Yan, Richard Azuah, Assad Sakhel, Jonathan DuBois, and Henry Glyde.

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