Comparative study of the binary icosahedral quasicrystalCd5.7Yband its crystalline approximantCd6Ybby low-temperature ultrahigh-resolution photoemission spectroscopy

Abstract

Low-temperature ultrahigh-resolution photoemission (PE) spectroscopy of the recently discovered binary icosahedral (i) ${\mathrm{Cd}}_{5.7}\mathrm{Yb}$ and its 1/1-cubic approximant Cd${}_{6}$Yb has commonly revealed a sharp Fermi edge with a marked spectral intensity decrease towards the Fermi level ${(E}_{F}),$ indicating the presence of a dip near ${E}_{F}$ which is consistent with the recent result of electronic structure calculations [Y. Ishii and T. Fujiwara, Phys. Rev. Lett. 87, 206408 (2001)], and the dip at ${E}_{F}$ is found to be much deeper in $i\ensuremath{-}{\mathrm{Cd}}_{5.7}\mathrm{Yb}$ than in $1/1\ensuremath{-}{\mathrm{Cd}}_{6}\mathrm{Yb}.$ Moreover, surface core-level shifts (SCS's) are clearly observed in the quasicrystal and the approximant, and the SCS's are found to be substantially different between these two compounds of different long-range orders.