Electronic structure of the topmost tenfold surface of decagonal Al-Ni-Co quasicrystal

Abstract

The electronic structure of the tenfold surface of a decagonal Al-Ni-Co quasicrystal was investigated using metastable ${\mathrm{He}}^{*}(2\phantom{\rule{0.2em}{0ex}}^{3}S,1s2s)$ deexcitation spectroscopy, which is extremely sensitive to the topmost surface. It was found that the density of states at the Fermi level was remarkably reduced at the topmost surface. The deexcitation of ${\mathrm{He}}^{*}$ via a resonance transition followed by Auger neutralization observed on the quasicrystalline surface indicates the persistence of states within the pseudogap at the topmost surface. The similarity of the electronic structure between the topmost surface and the bulk is consistent with a bulk-terminated structure, as observed by low-energy ion scattering spectroscopy.