When illuminated by laser light, assorted colloidal particles can arrange themselves into highly ordered structures called quasicrystals. By changing the phases of the lasers, researchers can force the colloids to further rearrange themselves in different ways. These collective rearrangements occur due to phasons, one of the many unique properties of quasicrystals.
Although scientists have observed the effects of phasons in quasicrystals, there are two different ways to theoretically describe what a phason is. Now in a new study, physicists have presented a way to look at phasons that links the two descriptions, providing a clearer picture of this unusual atomic motion that contributes to the uniqueness of quasicrystals.
The physicists, Justus A. Kromer and Holger Stark from the Berlin Institute of Technology, Michael Schmiedeberg from Heinrich Heine University in Dusseldorf, Germany, and Johannes Roth from the University of Stuttgart, have published their paper on phasons in a recent issue of Physical Review Letters.
Quasicrystals have intrigued scientists ever since they were discovered by materials scientist Dan Shechtman in 1982, for which he won the 2011 Nobel Prize in Chemistry. They are unusual in that they have order, but – unlike conventional crystals – they are not periodic, and so do not have translational symmetry. The result is a structure with an elegant-looking and complex atomic pattern.
Phasons are one of many properties of quasicrystals that do not exist in conventional crystals, but there are a couple different ways to theoretically describe them. Using fluid dynamics theory, scientists can describe phasons as a hydrodynamic mode, or a continuous pattern of motion. In this view, phasons might be thought of as a pattern of motion in which atoms rearrange themselves, similar to how phonons are described as a pattern of motion in which atoms vibrate (back and forth motion).