Tunneling spectroscopy in quasicrystals

We present tunneling spectroscopy measurements for icosahedral i-AlPdRe, i-AlCuFe and approximant α-AlMnSi phases. We show that for both oxidized and bare surfaces the density of states (DOS) close to the Fermi level exhibits specific features for quasicrystals and approximants as compared with the crystalline non approximant ω-AlCuFe phase. The Fermi energy lies in the middle of a narrow pseudo-gap of about 50 meV width. For higher energies, the DOS varies as the square root of energy, which is attributed to electron-electron interaction. The overall DOS differs from ab initio calculations and the possible roles of electron scattering and non homogeneous electronic structure close to the surface are discussed.