Superconductivity or superfluidity is generally associated with the appearance of a gap in the energ

1
CAREER Nature of Pure and Dirty Liquid 3He -
Fundamental Investigations and Educational
ActivitiesYoonseok Lee, University of Florida,
DMR-0239483
Gapless Superfluid
Superconductivity or superfluidity is generally
associated with the appearance of a gap in the
energy spectrum. However, in the presence of
disorder or impurity, superfluidity manifests
without a clean energy gap. This is the result
of impurity scattering whose effect is much more
pronounced in an unconventional pairing
superfluid such as superfluid phases of 3He. Our
high frequency sound attenuation measurements
down to zero temperature limit (200 microkelvin)
in the superfluid phase of 3He impregnated in
high porosity silica aerogel revealed completely
different behavior in comparison with the pure
superfluid phases. One of them is gapless
superfluidity. H.C. Choi et al., Phys. Rev. Lett.
98, 225301 (2007).
This figure shows the zero temperature sound
attenuation (ao) normalized by normal state
attenuation (ac) for various pressures (red
circles). Blue symbols represent the density of
state at zero energy, n(0) estimated from the
measurement. All quantities converge toward
normal state value at around 7 bars where the
superfluidity is extinguished. For P gt 7 bars
n(0) remains fairly high indicating gapless
superfluidity.
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CAREER Nature of Pure and Dirty Liquid
3He-Fundamental Investigations and Educational
ActivitiesYoonseok Lee, University of Florida,
DMR-0239483
OUTREACH PI hosted several laboratory tours
of PIs own Lab and the Microkelvin Laboratory of
University of Florida as the Director of the
facility (e.g. through the Science Quest Program
at UF). PI also gave 3 lectures with science
demos for three 6th grade classes at the Kanapaha
Middle School, Gainesville (December 7, 2006).
It is the 4th event since 2003. The 1 hour-long
session starts with a 10 min introduction on the
states of matter followed by interactive science
demos. About 70 6th grade students participated
in three separate sessions. PI also serves as
a judge for local science fairs every year. In
2006, Lincoln Middle School and Hawthorne High
School.
Some of the letters from the students. Student
names are partially altered for privacy.