Colloquia

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. These measurements have been replicated in four other laboratories. Specific heat results will also be discussed. This work is done in collaboration with Eunseong Kim, Tony Clark, Xi Lin and Josh West and it is supported by the (U.S.) National Science Foundation.