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Reminiscences of Jurgen Frank Alberta and Delaware

Reminiscences of Jurgen Frank Alberta and Delaware. CAP Annual Congress Charlottetown June 2003. Excitations, Bose-Einstein Condensation and Superfluidity in Liquid 4 He. Henry R. Glyde Department of Physics & Astronomy University of Delaware. CAP Annual Congress Charlottetown

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Reminiscences of Jurgen Frank Alberta and Delaware

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  1. Reminiscences of Jurgen FrankAlberta and Delaware CAP Annual Congress Charlottetown June 2003

  2. Excitations, Bose-EinsteinCondensation and Superfluidity in Liquid 4He Henry R. Glyde Department of Physics & Astronomy University of Delaware CAP Annual Congress Charlottetown June 2003

  3. Jurgen Franck

  4. Jurgen Franck

  5. Phase Diagram of Helium

  6. Lab Notes: JPF at Delaware

  7. Quantum Fluids and Solids Conference 1986

  8. Quantum Fluids and Solids Conference 1986

  9. Jurgen Franck

  10. Goals • Neutron scattering studies of excitations of quantum liquids in disorder. • phonons and rotons in disorder • new excitations in disorder • Reveal the interdependence of Bose-Einstein Condensation (BEC), phonon-roton excitations, and superfluidity. • Compare bulk liquid 4He and 4He in porous media (confinement and disorder).

  11. Bosons in Disorder Liquid 4He in Aerogel, Vycor, Geltech Flux Lines in High Tc Superconductors Josephson Junction Arrays Granular Metal Films Cooper Pairs in High Tc Superconductors Models of Disorder excitation changes new excitations at low energy Localization of Bose-Einstein Condensation by Disorder

  12. Superfluid Properties in Confinement/Disorder Confinement reduces Tc below . Confinement modifies (T dependence). Confinement reduces (magnitude). Porous media is a “laboratory” to investigate the relation between superfluidity, excitations, and BEC. Measure corresponding excitations and condensate fraction, no(T). (new, 1995)

  13. BEC, Excitations, and Superfluidity

  14. Excitations, BEC, and Superfluidity Collaborators: Francesco Albergamo - Institut Laue Langevin Grenoble, France Richard T. Azuah - NIST Center for Neutron Research Gaithersburg, Maryland, USA Jacques Bossy - Centre de Recherche sur Les Très Basses Temperature CNRS Grenoble, France Bjorn Fåk - ISIS Facility Rutherford Appleton Lab United Kingdom and Commissariat à l’Energie Atomique Grenoble, France

  15. Excitations, BEC, and Superfluidity Collaborators (Con’t): Oliver Plantevin - European Synchrotron Radiation Facility, Grenoble Gerrit Coddens - Laboratoire des solides irradiés Ecole Polytechnique Palaiseau, France Reinhard Scherm - Physikalisch-Technische Bundesanstalt, Braunschweig Norbert Mulders - University of Delaware Newark, Delaware USA John Beamish - University of Alberta Edmonton, Canada Helmut Schober - Institut Laue Langevin Grenoble, France

  16. Neutron Scattering: ILL

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

  18. Superfluid Density s(T) Bulk Liquid 4He Superfluid Density

  19. London

  20. Superfluid Density in Porous Media Chan et al. (1988) Miyamoto and Takeno (1996) Geltech (25 Å pores)

  21. Bose-Einstein Condensation Glyde, Azuah, and Sterling Phys. Rev., 62, 14337 (2001)

  22. Bose-Einstein Condensation: Atoms in Traps

  23. Bose-Einstein Condensation: Atoms in Traps

  24. Bose-Einstein Condensation Condensate Fraction

  25. Bose-Einstein CondensationLiquid 4He in Vycor Tc (Superfluidity) = 1.95-2.05 K Azuah et al., JLTP (2003)

  26. Bose-Einstein CondensationLiquid 4He in Vycor Tc (Superfluidity) = 1.95-2.05 K Azuah et al., JLTP (2003)

  27. Phonon-Roton Dispersion Curve  Donnelly et al.,J. Low Temp. Phys. (1981)  Glyde et al.,Euro Phys. Lett. (1998)

  28. Phonons and Rotons Arise From Bose-Einstein Condensation Bogoliubov (1947) showed: Bose gas with BEC -- quasiparticles have energy: - phonon (sound) form Quasiparticle mode coincides with sound mode. Only one excitation when have BEC.

  29. Phonons and Rotons Arise From Bose-Einstein Condensation Gavoret and Nozières (1964) showed: Dense liquid with BEC – only one excitation: density and quasiparticle modes have the same energy, At low Q, as in Bose gas. No other excitations at low energy (could have vortices). Ma and Woo (1967), Griffin and Cheung (1973), and others showed: Only a single mode at all Q with BEC -- the phonon-roton mode.

  30. Landau

  31. Superfluidity Landau Theory Superfluidity follows from the nature of the excitations: that there are phonon-roton excitations only and no other low energy excitations to which superfluid can decay have a critical velocity and an energy gap (roton gap ). Via P-R excitations, superflow arises from BEC. BEC and Phase Coherence, Ø (r) Superfluidity follows directly from BEC, phase conherence .

  32. Maxon in Bulk Liquid 4He Talbot et al., PRB, 38, 11229 (1988)

  33. Roton in Bulk Liquid 4He Talbot et al., PRB, 38, 11229 (1988)

  34. Beyond the Roton in Bulk Liquid 4He

  35. Excitations, BEC, and Superfluidity Bulk Liquid 4He BEC, well-defined excitations and superfluidity coincide e.g., all have some critical temperature, = 2.17 K SVP = 1.92 K 20 bar

  36. BEC, Excitations, and Superfluidity

  37. Excitations in a Bose Fluid

  38. Superfluid Properties in Confinement/Disorder Confinement reduces Tc below . Confinement modifies (T dependence). Confinement reduces (magnitude). Porous media is a “laboratory” to investigate the relation between superfluidity, excitations, and BEC. Measure corresponding excitations and condensate fraction, no(T). (new, 1995)

  39. Porous Media • AEROGEL 95% porous • 87% porous A • 87% porous B • -- grown with deuterated materials or flushed with D2 • VYCOR 30% porous • 70 diameter pores • -- grown with B11 isotope • GELTECH SILICA 50% porous • 25 diameter pores • -- flushed with D2

  40. Tc in Porous Media

  41. Phonons, Rotons, and Layer Modes in Vycor and Aerogel

  42. Temperature Dependenceof Roton Energy Fåket al., PRL, 85 (2000)

  43. Layer Mode in Vycor and Aerogel

  44. Intensity in Single Excitation vs. T Glyde et al., PRL, 84 (2000)

  45. Phonon-Roton Mode in Vycor:T = 2.05 K

  46. Fraction, fs(T), of Total Scattering Intensity in Phonon-Roton Mode

  47. Roton in Geltech Silica: Partial Filling Plantevin et al., PRB, 65 (2002)

  48. Liquid 4He in Geltech Silica Tc (Superfluidity) = 0.725 K

  49. Excitations, BEC, and Superfluidity Liquid 4He in disorder BEC, well-defined excitations and separated from superfluidity in disorder e.g., Tc - superfluidity Tc(BEC) - Bose-Einstein condensation Tc(BEC) > Tc Disorder localizes the condensate. New Here Measurements of phonon-roton excitations and BEC in disorder

  50. BEC in Disorder Both no and reduced by static disorder (homogeneous). Huang & Meng, PR 1992 dilute gas limit, analytic Astraljparehik, et al., preprint (2002) fluid densities, Monte Carlo reduced more than no Could have localized BEC. As T is reduced, BEC forms first in favorable regions, in pockets. Superflow occurs at a lower T when regions grow and connect to have phase coherence across the entire sample.

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