Electronic structure of quasicrystals studied by ultrahigh-energy-resolution photoemission spectroscopy

The results of low-temperature, ultrahigh-resolution ultraviolet photoemission studies of the electronic structure of stable icosahedral (Formula presented)(Formula presented)(Formula presented), (Formula presented)(Formula presented)(Formula presented), (Formula presented)(Formula presented)(Formula presented), (Formula presented)(Formula presented)(Formula presented)(Formula presented), (Formula presented)(Formula presented)(Formula presented), (Formula presented)(Formula presented)(Formula presented), (Formula presented)(Formula presented)(Formula presented)(Formula presented), (Formula presented)(Formula presented)(Formula presented), and (Formula presented)(Formula presented)(Formula presented), decagonal (Formula presented)(Formula presented)(Formula presented) and (Formula presented)(Formula presented)(Formula presented), and crystalline (Formula presented)(Formula presented)Ru and (Formula presented)MnAl alloys are presented. It is shown that these alloys have a clearly developed Fermi edge, and are thus metallic down to the temperature of measurement (12-45 K). A marked decrease of the spectral intensity toward the Fermi level in quasicrystals is demonstrated to be consistent with the existence of the theoretically predicted pseudogap. With an experimental resolution of 5 meV, no evidence of the theoretically predicted spikiness of the density of states could be observed. A close similarity between the values and unusual dependencies of various physical parameters observed in quasicrystals and in their approximants suggests that they are not the consequence of the long-range quasiperiodicity, but rather result from a complex local atomic order. A review of the electronic properties of quasicrystals is also presented.