NMR study of the electronic properties and stability of quasicrystals

We have studied by NMR the electronic properties of the stable quasicrystalline phases ${\mathrm{Al}}_{57}$ ${\mathrm{Cu}}_{10.8}$ ${\mathrm{Li}}_{32.2}$ and ${\mathrm{Al}}_{62}$ ${\mathrm{Cu}}_{25.5}$ ${\mathrm{Fe}}_{12.5}$ and of two crystalline approximants, the bcc R phase ${\mathrm{Al}}_{56}$ ${\mathrm{Cu}}_{12}$ ${\mathrm{Li}}_{32}$ and the rhombohedral ${\mathrm{Al}}_{62.8}$ ${\mathrm{Cu}}_{26}$ ${\mathrm{Fe}}_{11.2}$ phase. Low values of the density of states at the Fermi level are observed in the crystalline as well as in the quasicrystalline phases. The existence of a pseudogap at the Fermi level is therefore not a consequence of the quasiperiodicity. These results renew the debate on the stability of quasicrystals.