Melting curve of 4^4He: no sign of the supersolid transition down to 10 mK

We have measured the melting curve of $^4$He in the temperature range from 10 to 400 mK with the accuracy of about 0.5 $\mu$bar. Crystals of different quality show the expected $T^4$-dependence in the range from 80 to 400 mK without any sign of the supersolid transition, and the coefficient is in excellent agreement with available data on the sound velocity in liquid $^4$He and on the Debye temperature of solid $^4$He. Below 80 mK we have observed a small deviation from $T^4$-dependence which however cannot be attributed to the supersolid transition because instead of decrease the entropy of the solid rather remains constant, about $2.5\times10^{-6}$ $R$Comment: 4 pages, 2 figures, published in Physical Review Letter

Experimental setup for the observation of crystallization waves in He-3

At low temperatures helium crystals can grow and melt so fast that a meltingfreezing wave may propagate along the liquid-solid interface. In He-4 these crystallization waves have been observed at temperatures below 0.5 K. The required temperature for the observation of the crystallization waves in He-3 is predicted to be about 0.2 mK. In order to reach such low temperature at the melting pressure of He-3, special care has to be taken in the design of the experimental cell. Here we present the draft of the experimental cell which is designed for observation of the crystallization waves in He-3

Cavitation in superfluid helium-4 at low temperature

We have studied the nucleation of bubbles in pure superfluid helium-4 at temperatures down to 65 mK. We have found that the nucleation is a stochastic process, and that at temperatures below 600 mK the nucleation rate is independent of temperature. These results are consistent with the assumption that the nucleation takes place via quantum tunneling