PHYSICS AND ASTRONOMY COLLOQUIUM

Thursday, November 30, 2006
4:10 p.m.

1415 Biomedical & Physical Sciences Bldg.
Refreshments at 3:30 pm in Rm. 1400 BPS Bldg

Speaker: Moses Chan
         Pennsylvania State University

Title:   Can a Solid be "Superfluid"?

Abstract: 

At temperatures below 2.176K, liquid He-4 enters into a superfluid state
and flows without any friction.  The onset of superfluidity is associated
with Bose-Einstein condensation where the He-4 atoms, which are bosons,
condensed into a single momentum state and acquire quantum mechanical
coherence over macroscopic distances.  Recent torsional oscillator
measurements of solid helium confined in porous media [1,2] and in bulk
form [3,4] found evidence of non-classical rotational inertia indicating
superfluid behavior below 0.2K.  Measurements of solid samples at
different pressure (and hence different density) allow us to map out the
boundary of this supersolid phase.  This work is done in collaboration
with Euneseong Kim, Tony Clark, Xi Lin and Josh West and it is supported
by the (U.S.) National Science Foundation.