Squeezing Superfluid from a Stone: Coupling Superfluidity and Elasticity in a Supersolid

Superfluidity - the ability of liquid 4He, when cooled below 2.176 K, to flow without resistance through narrow pores - is one of the most amazing phenomena in physics. Supersolidity - the coexistence of superfluid behavior with the crystalline order of a solid - was proposed theoretically long ago as an even more exotic phase of solid 4He, but it has eluded detection until recently. In 2004, Kim and Chan (E. Kim and M. H. W. Chan, Nature (London) 427, 225 (2004); E. Kim and M. H. W. Chan, Science 305, 1941 (2004).) reported the onset of "nonclassical rotational inertia" in a torsional oscillator experiment with solid 4He, and they interpret their results as indicating the onset of supersolidity. In this talk, I'll describe what a supersolid is, discuss the Chan et al experiments (in the process revealing how to tell a raw from a hard boiled egg), and present the theory I've recently developed (with Paul Goldbart of University of Illinois at Urbana-Champaign, and Alan Dorsey of University of Florida) of the normal solid to supersolid (NS-SS) phase transition.