Finite-temperature elasticity phase transition in decagonal quasicrystals

We present evidence for a finite-temperature phase transition in the phason elasticity of quasicrystals. A tiling model for energetically stabilized decagonal quasicrystals has been studied in an extensive series of Monte Carlo simulations. The Hamiltonian (energetics) of the model is given by nearest-neighbor Penrose-like matching rules between three-dimensional unit cells. A new order parameter and diagnostics have been introduced. We show that a transition from locked-phason to unlocked-phason dynamics occurs at finite temperature. In the unlocked phase, phasons can be thermodynamically excited even though the quasicrystal is energetically stabilized at low temperatures.