Crystallization ofHe4in aerogel via mass flow from surrounding solidHe4

What is it about?

Our finding of crystallization of 4He in aerogels by cooling indicates that the crystallization and the “supersolidity” of surrounding crystals were closely connected. It provided a clue to solve the contradiction of the mass flow experiments in 4He crystals. Independent control of pressure and temperature in unexplored low temperature region also revealed fine structures of the crystal-superfluid diagram such as the unexpected maximum in the temperature dependence of the crystallization pressure.

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Why is it important?

We succeeded in determining the crystallization diagram of 4He in aerogels in unexplored low temperature region and discovered that the crystallization in the aerogels was closely connected to the possible supersolidity of the surrounding bulk 4He crystals. Utilizing a variable-volume cell which has never been used for studying the crystallization of 4He in porous materials, independent control of the pressure and temperature became possible and detail of the crystallization process in aerogel was revealed at very low temperatures.