Measurements of the Dielectric Constant of Solid Helium at Low Temperatures

A careful measurement of the dielectric constant of solid He-4 was made to search for signatures associated with the reported onset of nonclassical rotational inertia and shear modulus stiffening. The samples studied include zero-pressure liquid, solid-liquid mixtures on the melting-curve and solid helium. It was found that the dielectric constant of solid He-4 decreases smoothly with temperature below 300 mK, showing no measurable anomalies down to 50 mK. The new measurements do not show the anomalous upturn effect that was reported in our previous measurements.