Bose-Einstein Condensation, Superfluidity and Elementary Excitations in Quantum Liquids

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• Prof. Henry Glyde, University of Delaware
• Friday 21 November 2014, 14:00-15:00
• Physics East 217.

If you have a question about this talk, please contact Elizabeth Blackburn.

Helium was first liquefied in 1908 in the famous Kamerlingh Onnes laboratories in Leiden. In the ensuing 105 years, liquid helium has displayed a rich spectrum of novel properties such as Bose-Einstein condensation (BEC), superfluidity and sharply defined elementary excitations with many parallels with superconductors. These properties and the physics of liquid helium will be surveyed with the aim of articulating the interdependence of BEC , excitations and superfluidity. Neutron scattering measurements have brought unique data on both BEC and the characteristic phonon-roton (P-R) excitations. Particularly we survey recent measurements of BEC and P-R modes in bulk and nanoscale confined helium which show that well-defined P-R modes exist only where there is BEC . In this sense the Landau and BEC theories of superfluidity have a common physical origin, BEC [1]. In addition, further comparison with superfluid density measurements shows that in porous media (in disorder) there is a localized BEC “phase” between the superfluid and normal phases, a “phase” in which there is BEC but no macroscopic superflow. This “phase” has analogies with the pseudogap phase in cuprate superconductors.

[1] Evidence for a common physical origin of the Landau and BEC theories of superfluidity, Diallo et al., Phys. Rev. Lett. November (2014).

This talk is part of the Condensed Matter Physics Seminars series.

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• Bham Talks
• Cond. Mat. seminar
• Condensed Matter Physics Seminars
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