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 a-AlMnSi phases reveal specific features of the density of states (DOS) close to the Fermi level as compared to the crystalline nonapproximant v-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.[S0031-9007(96)

Bulk electronic structure of Zn-Mg-Y and Zn-Mg-Dy icosahedral quasicrystals

“…[2][3][4][5] There is a growing body of theoretical and experimental evidence that the fundamental reason for the formation of quasicrystalline order is the presence of a pseudogap around the Fermi level. [6][7][8][9][10] However, the electronic contribution to the specific heat in Zn-Mg-Y was reported to be similar to Zn metal, indicating no reduction of the density of states (DOS) at E F , 4 although in the same work a distinct feature that was assigned to an excitation across a pseudogap was observed from optical conductivity study. 4 It was also reported 11 that their resistivity (150-200 µΩ-cm) is an order of magnitude lower than Al-based quasicrystals such as Al-Pd-Mn 12 or highly conducting compositions of Al-Pd-Re, 13 again pointing towards a higher DOS at E F in the former.…”

Unoccupied electronic states of icosahedral Al-Pd-Mn quasicrystals: Evidence of image potential resonance and pseudogap

“…The formation of a pseudogap near the Fermi level (E F ) has been related to a Fermi surface-quasi Brillouin zone interaction mechanism. 1,2 An increasing body of evidence has supported this notion 3,4 indicating the presence of a pseudogap in the bulk, while the surface may behave differently. 5,6 The bulk electronic structure of quasicrystals recently studied by hard x-ray photoelectron spectroscopy demonstrates presence of a pseudogap.…”

Optimizing the thermoelectric efficiency of icosahedral quasicrystals and related complex alloys

“…1͒ agrees well with the experimental results obtained from tunneling and point contact spectroscopy measurements, where the presence of a dip feature of small width ͑20-60 meV͒, superimposed onto a broad ͑0.5-1 eV͒ asymmetric pseudogap, has been reported. 23,[31][32][33] Thus, Eq. ͑2͒ satisfactorily describes the electronic structure of these alloys in terms of a wide Lorentzian peak ͑related to the Fermi surface-Brillouin zone interaction͒ plus a narrow Lorentzian peak ͑related to sp-d hybridization effects͒.…”