Density of States in Quasicrystals and Approximants: Tunneling Experiment on Bare and Oxidized Surfaces

Abstract

Tunneling spectroscopy studies on oxidized and bare surfaces of icosahedral i-AlPdRe, i-AlCuFe, and approximant $\ensuremath{\alpha}$-AlMnSi phases reveal specific features of the density of states (DOS) close to the Fermi level as compared to the crystalline nonapproximant $\ensuremath{\omega}$-AlCuFe phase. The Fermi energy lies in the middle of a narrow pseudogap of about 50 meV width. For higher energies, the DOS exhibits a square root energy dependence attributed to electron-electron interaction effects. The DOS differs from the linear muffin tin orbital calculated DOS and the possible roles of electron scattering and inhomogeneous electronic structure close to the surface are discussed.