Observation of a glassy phase ofHe4in the region of supersolid effects

Abstract

High-precision pressure measurements in solid $^{4}\mathrm{He}$, grown by the capillary blocking technique, have been made in temperatures range from $50\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}500\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$. The temperature dependence of pressure indicates that aside from the usual phonon contribution $\ensuremath{\sim}{T\phantom{\rule{0.1em}{0ex}}}^{4}$, there is an additional contribution $\ensuremath{\sim}{T\phantom{\rule{0.1em}{0ex}}}^{2}$, the latter becoming dominant at temperatures $T<300\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$, where an abnormal behavior attributed to supersolidity has been observed. The data suggest the appearance of a glassy phase (that might be responsible for the anomalous behaviors observed previously). A dramatic pressure decrease has been observed under annealing of the samples. The glassy contribution to the pressure can be eliminated in well-annealed crystals.