A non-superfluid origin of the non-classical rotational inertia in a bulk sample of solid 4He

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