Anomalously slow strain relaxation in quasicrystals and conventional crystals

The slow time dependence of the elastic response of quasicrystals is calculated in detail. The response, which is isotropic for short times, becomes anisotropic in a way that reflects the icosahedral symmetry once phasons have had time to diffuse across the sample. The initial response grows as st. This slow stress relaxation is the simplest macroscopic experimental signature of quasicrystalline order. Analogous but far smaller phenomena are also shown to occur in conventional crystalsa heretofore unrecognized property of ordinary elastic dynamics. © 1988 The American Physical Society.