Observation of Classical Rotational Inertia and Nonclassical Supersolid Signals in Solid He4 below 250mK

We have confirmed the existence, as first reported by Kim and Chan, of a supersolid state in solid He4 at temperatures below 250 mK. We have employed a torsional oscillator cell with a square cross section to insure a locking of the solid to the oscillating cell. We find that the nonclassical rotational inertia signal is not a universal property of solid He4 but can be eliminated through an annealing of the solid helium sample. This result has important implications for our understanding of the supersolid state.