Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 6: Electronic structure I
O 6.3: Vortrag
Montag, 23. März 2009, 11:45–12:00, SCH A216
Valence level bands and Fermi surface of decagonal Al-Cu-Co — Wolfgang Theis1, Jan Hugo Dil2, Ajay Shukla3, JeongWon Kim3, Hoon Koh4, Eli Rotenberg4, Peter Gille5, and •Karsten Horn2 — 1Fachbereich Physik, FU Berlin, D — 2Fritz Haber Institute of the MPG, Berlin, D — 3UGC-DAE-CSR, Indore, India — 4ALS, Lawrence Berkeley Lab, USA — 5Dpt. Geosciences, LMU Munich, D
Valence electronic states in quasicrystals seem to defy the concept of Bloch states because of the absence of translational periodicity. However, this may not necessarily preclude the existence of delocalized electronic states in quasicrystals, since critical electronic states which fall off with a power law may exist, and evidence for delocalized states has been found in quasicrystals in the region of the deeper valence bands. For an analysis of the transport properties of quasicrystals an investigation of the region near the Fermi level is important, however, Here we examine the s-p-derived electronic structure of decagonal Al-Cu-Co in this region using angle-resolved photoemission. These states are accessible in Al-Cu-Co because, unlike in Al-Ni-Co, the d bands are well removed and do not interfere. We find that the electronic structure can be well represented by parabolic dispersing bands in a region of about 1 eV below the Fermi level. The data are analyzed within a model that uses a subset of specific reciprocal lattice vectors, and that provides a consistent description of the photoemission intensity distribution and the dispersion of the observed state signatures.