Excitations, Bose-Einstein Condensation in addition to Superfluidity in Liquid 4He

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Excitations, Bose-Einstein Condensation in addition to Superfluidity in Liquid 4He

Parsons, Russ, Food Contributor has reference to this Academic Journal, PHwiki organized this Journal Excitations, Bose-Einstein Condensation in addition to Superfluidity in Liquid 4He Henry R. Glyde Department of Physics & Astronomy University of Delaware Phase Diagram of Helium Goals Neutron scattering studies of excitations of quantum liquids in disorder. phonons in addition to rotons in disorder new excitations in disorder Reveal the interdependence of Bose-Einstein Condensation (BEC), phonon-roton excitations, in addition to superfluidity. Compare bulk liquid 4He in addition to 4He in porous media (confinement in addition to disorder).

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Phonon-Roton Dispersion Curve Donnelly et al., J. Low Temp. Phys. (1981) Glyde et al., Euro Phys. Lett. (1998) 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 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, in addition to BEC. Measure corresponding excitations in addition to condensate fraction, no(T). (new, 1995)

Graduate Students Jonathan DuBois Bose-Einstein Condensation of Bosons in Traps, Variational Monte Carlo, Diffusion MC Asaad Sakhel Models of excitations in liquid 4He BEC in traps Ali Shams Souleymane Omar Diallo Excitations, BEC, in addition to Superfluidity Collaborators: Francesco Albergamo – Institut Laue Langevin Grenoble, France Richard T. Azuah – NIST Center as long as Neutron Research Gaithersburg, Maryl in addition to , USA Jacques Bossy – Centre de Recherche sur Les Très Basses Temperature CNRS Grenoble, France Bjorn Fåk – ISIS Facility Ruther as long as d Appleton Lab United Kingdom in addition to Commissariat à l’Energie Atomique Grenoble, France Excitations, BEC, in addition to 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

Neutron Scattering Laboratories Institute Laue Langevin Grenoble, France ISIS Ruther as long as d Appleton Laboratories Ox as long as dshire, Engl in addition to NIST Center as long as Neutron Research National Institute of St in addition to ards in addition to Technology Gaithersburg, Maryl in addition to Neutron Scattering: ILL Excitations in addition to Bose-Einstein Condensation in Quantum Liquids in Disorder Henry 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 in addition to Olivier Plantevin in front of the IN6 neutron spectrometer of ILL.

Bose-Einstein Condensation: Atoms in Traps Bose-Einstein Condensation: Atoms in Traps Bose-Einstein Condensation Glyde, Azuah, in addition to Sterling Phys. Rev., 62, 14337 (2001)

Bose-Einstein Condensation Condensate Fraction Tc in Porous Media Superfluid Density s(T) Superfluid Density Bulk Liquid 4He

London BEC, Excitations, in addition to Superfluidity L in addition to au

Phonon-Roton Dispersion Curve Donnelly et al., J. Low Temp. Phys. (1981) Glyde et al., Euro Phys. Lett. (1998) Superfluidity L in addition to au Theory Superfluidity follows from the nature of the excitations: that there are phonon-roton excitations only in addition to no other low energy excitations to which superfluid can decay have a critical velocity in addition to an energy gap (roton gap ). Via P-R excitations, superflow arises from BEC. BEC in addition to Phase Coherence, Ø (r) Superfluidity follows directly from BEC, phase conherence . Phonons in addition to Rotons Arise From Bose-Einstein Condensation Gavoret in addition to Nozières (1964) showed: Dense liquid with BEC – only one excitation: density in addition to quasiparticle modes have the same energy, At low Q, as in Bose gas. No other excitations at low energy (could have vortices). Ma in addition to Woo (1967), Griffin in addition to Cheung (1973), in addition to others showed: Only a single mode at all Q with BEC – the phonon-roton mode.

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

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

Localization of Bose-Einstein Condensation by Disorder Henry Glyde, University of Delaware, Oscar Vilches, University of Washington, John Larese, University of Tennessee Focused Research Group, DMR-0115663 Our neutron scattering studies of liquid 4He in porous media show evidence of Bose-Einstein Condensation localized by disorder. In bulk, pure systems the origin of superfluidity ( in addition to superconductivity) is BEC. Once there is BEC, there are simultaneously phonon-roton excitations in addition to superfluidity. In contrast, in disorder the BEC can be localized so that there are P-R excitations but no macroscopic superfluidity. Superfluidity follows at a lower temperature when the BEC becomes extended across the sample. The “localized BEC” state in liquid 4He is similar to the “pseudo gap” state observed in high Tc superconductors.

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