Indication of van Hove singularities in the density of states of ZnMg(Y,Ho) quasicrystals

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

“…This may well be the reason why in these studies, a pseudogap was not observed in icosahedral (i)-Zn-Mg-Y by Stadnik et al; 2 rather a clear existence of a metallic Fermi edge was established, with a linearly decreasing intensity from higher binding energies towards E F . Suchodolskis et al, 5 working on single grain i-Zn-Mg-Y, also observed a metallic Fermi edge. On the other hand, the DOS calculations using density functional theory for a hexagonal approximant to Zn-Mg-Y showed the existence of a pronounced pseudogap around the Fermi level, due to a strong hybridization between the s and p -d states related to Y.…”

“…Since photoelectron spectroscopy is a direct probe of the electron states, the pseudogap has been studied extensively using this technique, albeit with low photon energies (ultra violet to soft x-ray range) that provided information about the surface electronic structure because of the small escape depth of photoelectrons with low kinetic energy. 2,5,14,15 This surface sensitivity may give rise to erroneous conclusions because the surface structure may deviate from that of the bulk, giving rise to a change in electronic structure. This may well be the reason why in these studies, a pseudogap was not observed in icosahedral (i)-Zn-Mg-Y by Stadnik et al; 2 rather a clear existence of a metallic Fermi edge was established, with a linearly decreasing intensity from higher binding energies towards E F .…”

“…10 The present work resolves the continuing disagreement between ab initio density functional theory and the results from surface sensitive photoemission spectroscopy. 2,5 …”

“…[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.…”

Interband optical transitions of Zn

“…Results of the calculations, carried out following the algorithm described in Ref. [21] for gap values of Δ 002 = 0.9 eV and Δ 101 = 1.54 eV, are presented in Fig. 7.…”