Controlling the symmetry of xenon crystals by repetitive heating

Stationary free growth of xenon crystals into homogeneous undercooled melt leads to a morphology which can be characterized by a side branching frequency depending on undercooling. The dendrites are statistically symmetric and their contours have a characteristic fractal dimension. In a new non-steady-state experiment we cycle temperature to at most slightly above the melting temperature and back to an initially given undercooling. The morphology of a perturbed crystal differs from the morphology of a typical steady-state dendrite. Four absolutely symmetrical lobes start to grow at the main tip and develop into dominant side branches after each cycle. Repeating the melting cycle leads to a controlled formation of the side branches and finally to symmetric tree-like crystals in three-dimensional. Their contours are found to have a lower fractal dimension and show lower curvatures than the ones known for stationary free growth.