2020 Volume 47 Issue 4 Article ID: 47-4-03
Crystallization of 4He quantum crystals in superfluid advances very rapidly at low temperatures owing to the fast mass transport via superflow and the negligibly small latent heat. Rapid crystallization allows the fundamental physics of crystal shape and growth to be explored in a measurable time scale in laboratories and the peculiar interfacial phenomena such as the crystallization wave propagation to be realized. Rapid crystallization also means that 4He crystals can response to tiny driving forces which have been neglected for ordinary classical crystals. Here, we report the effects of novel driving forces, such as gravity change, superflow, wettability and acoustic radiation pressure. Subjected to these driving, 4He crystals were strongly deformed and brought to highly non-equilibrium states, showing various kinds of extraordinary crystallization and relaxation processes in the superfluid. Furthermore, huge 4He crystals were successfully obtained in zero gravity and their shape was analyzed by the theory of equilibrium shapes.