Ultracold, trapped quantum gases have gained prominence
in recent years as systems where fundamental theories of many-body
physics can be tested in a clean environment with "tunable"
parameters. One of the most exciting prospects is the possibility
of observing second sound in a strongly interacting Fermi gas
superfluid. Never found (so far) outside quantum liquids, second
sound is a pure temperature wave: a collective hydrodynamic mode
that has no analogue in classical, non-superfluid liquids.
mode is quite different in trapped Fermi gases than in liquid Helium. In this talk, I discuss the nature
of second sound in these gases and outline a new scheme to excite and detect these modes.
Ref.: E. Taylor, H. Hu, X.-J. Liu, L. P. Pitaevskii, A. Griffin, and S. Stringari, arXiv:0905.0257