Macroscopic Quantum Tunneling and Avalanche Size Distribution of 4He Crystallization in Aerogel

What is it about?

We studied crystallization of superfluid 4He in silica-aerogels to see the effect of disorder on dynamics of the first order phase transition at very low temperatures. Avalanche size distribution was measured in the low temperature regime and the number of smaller avalanches was larger. The size distribution followed a power law in a length scale smaller than a large-scale cutoff size and thus the crystallization showed a criticality. While the exponent of the power law was nearly temperature independent, the cutoff decreased with warming toward the transition temperature.

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Why is it important?

The distribution had a temperature dependence, which implies that the crystallization under disorder showed the tuned criticality at such low temperatures.