A. D. Fefferman, X. Rojas, A. Haziot, S. Balibar, J. T. West, M. H. W. Chan
We have studied natural purity $^{4}$He single crystals and polycrystals
between 10 and 600 mK using a torsional oscillator with a 2 cm$^{3}$ rigid cell
made of sapphire with a smooth geometry. As the temperature was lowered, we
observed sample dependent but reproducible resonant frequency shifts that could
be attributed to a supersolid fraction of order 0.1%. However, these shifts
were observed with single crystals, not with polycrystals. Our results indicate
that, in our case, the rotational anomaly of solid helium is more likely due to
a change in stiffness than to supersolidity. This interpretation would
presumably require gliding of dislocations in more directions than previously
thought.
View original:
http://arxiv.org/abs/1112.5998
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