BoseEinstein condensation, excitations and superfluidity Henry Glyde, University of Delaware, Oscar

1
Bose-Einstein condensation, excitations and
superfluidityHenry Glyde, University of
Delaware, Oscar Vilches, University of
Washington,John Larese, University of Tennessee
FRG, Neutron Scattering DMR-0115663
The origin of superfluidity and
superconductivity, whether Bose-Einstein
condensation (BEC) or well defined excitations
(energy gap), remains to be clarified in many
circumstances. We are investigating liquid helium
confined to nanoscales in porous media using
neutron scattering. We find evidence for both
localization of BEC by disorder at saturated
vapor pressure (SVP) 1 and for loss of
excitations at higher pressure 2 being
responsible for loss of superflow. The schematic
figure opposite (top) shows the superfluid phase
in porous media. A possible quantum phase
transition to normal helium at p 3.2 MPa (32
bars) and T 0 K has been reported 3. The
figure opposite (below) shows loss of
phonon-roton modes at p gt 25.3 bars 2.
Phase diagram of 4He in porous media (dotted,
bulk)
.
Phonon-roton excitations under pressure
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Bose-Einstein condensation , excitations and
superfluidityHenry Glyde, University of
Delaware, Oscar Vilches, University of
Washington,John Larese, University of Tennessee
FRG, Neutron Scattering DMR-0115663
Education
Our neutron scattering program at US and European
neutron facilities involves several post doctoral
associates, graduate students and undergraduates.
It provides training using a wide spectrum of
neutron spectrometers at both reactor and
spallation based neutron sources as well as an
international research experience. Shown opposite
(top) is Richard Azuah, formerly a post doc now
on staff at the NIST Center for Neutron Research,
and Souleymane Omar Diallo (facing laptop),
currently a senior graduate student in the group.
.
1 H.R. Glyde et al. Phys. Rev. Lett. 84, 2646
(2000) F. Albergamo et al. Phys. Rev. B69,
014514 (2004). 2 J.V. Pearce et al. Phys. Rev.
Lett. 93, 1453303 (2004). 3 H. Yamamoto et al.
Phys. Rev. Lett. 93, 075302 (2004).