Phason-strain field and vibrational specific heat in icosahedral AlLiCu
Résumé
For an icosahedral system, phason-strain fields can be classified into two classes, transforming respectively under the Γ4 and Γ5 irreducible representations of the icosahedral group. Group theory predicts that the Γ4 phason-strain field, as the one observed in as-cast quasicrystalline AlLiCu samples, is not coupled to phonon modes. The low temperature specific heat of AlLiCu samples was measured after 10 days of annealing which allows phason-strain elimination and leads to almost perfect samples. No vibrational contribution evolution is observed. Some consequences and implications are discussed.