Nonsuperfluid Origin of the Nonclassical Rotational Inertia in a Bulk Sample of Solid 4He

The torsional oscillator experiments described here examine the effect of disorder on the nonclassical rotational inertia (NCRI) of a solid He-4 sample. The NCRI increases with increasing disorder, but the period changes responsible for this increase occur primarily at higher temperatures. Contrary to expectations based on a supersolid scenario, the oscillator period remains relatively unaffected at the lowest temperatures. This result points to a nonsuperfluid origin for the NCRI.