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Abstracts
T3
“Pure” superfluid
3
He, an introduction.
George Pickett
Lancaster University, UK
At millikelvin temperatures the Fermionic
3
He atoms in liquid couple to form
Cooper pairs to create superfluid
3
He. The Cooper pair has an angular moment
of
~
, in which the two component atoms orbit each other as a loosely-connected
dimer. Since the angular momentum is odd, to preserve parity, the spin must also
be odd, i.e. also
~
. This gives the Cooper pairs a very rich structure allowing the
existence of several phases with very different properties and provides a number of
handles for probing the condensate especially by NMR and quasiparticle “optics”.
An interesting regime is the very low temperature region, where the condensate
is essentially “pure” giving rise to a number of interesting properties and with a
wavefunction whose symmetry provides an interesting simulation of the metric
of the universe, allowing “tabletop” cosmological experiments.
T4
The Supersolid Story
Moses Chan
Penn State University, USA
Torsional oscillator (TO) measurements of solid
4
He carried out twelve years
ago found an abrupt drop in the resonant period (∆P) below 0.2K, suggesting
superfluid onset in the solid. However, subsequent studies indicate the ∆P is due
to the stiffening of the solid. New TO studies free of stiffening effect placed an
upper limit of superfluidity in solid of 5
×
10
−
6
. Interestingly this is not the last
word in supersolidity. By means of a clever design, Hallock found evidence of
superfluid-like mass flow through solid
4
He sandwiched between two superfluid
reservoirs. Recent experiments at UMass, Alberta and Penn State on the nature
of this mass flow will be discussed
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