PHASON-STRAIN-FIELD INFLUENCES ON LOW-TEMPERATURE SPECIFIC-HEAT IN ICOSAHEDRAL QUASI-CRYSTALS AL-LI-CU AND AL-FE-CU

We investigated the phason-strain-field influences on electronic and v ibrational properties of two icosahedral quasicrystals, Al-Li-Cu and A l-Fe-Cu. For that purpose we performed low-temperature specific-heat m easurements on samples before and after annealing treatments that allo wed strong phason-strain elimination. The electronic specific heat for the two systems is found to be scarcely sensitive to the annealing tr eatments, while the vibrational specific heat displays a different beh avior: it remains unchanged in Al-Li-Cu, but is strongly reduced in Al -Fe-Cu after annealing. We interpret this to arise from the correlatio n between the symmetry of the phason-strain field and the electronic a nd vibrational properties.