ELECTRONIC-STRUCTURE AND TRANSPORT IN A MODEL APPROXIMANT OF THE DECAGONAL QUASI-CRYSTAL AL-CU-CO

The electronic structure and conductivity in a model approximant Al66Cu30Co14 of decagonal quasicrystals Al-Cu-Co is presented theoretically. As in most quasicrystals and approximants, the density of states exhibits a well pronounced pseudogap at the Fermi level, commonly attributed to the Hume-Rothery phenomenon. From the local density of states and band dispersion, wave functions of eigenstates at the Fermi level are analyzed. They are very flat bands, located on a specific group of atoms, and of p-d symmetry. This suggests the importance of hybridization between transition metals and aluminum in quasicrystals. The intraband electronic conductivity at T = 0 K, calculated in Boltzmann theory, agrees quantitatively with experimental values. Its temperature dependence is also discussed. The strong anisotropy of decagonal phases has a crucial effect on all aspects of the electronic structure and then on transport properties and stability.