Regensburg 2004 – scientific programme
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O: Oberflächenphysik
O 17: Elektronische Struktur (Experiment und Theorie) II
O 17.4: Talk
Tuesday, March 9, 2004, 12:00–12:15, H36
Shockley surface states at close-packed surfaces — •Frederik Schiller1,2, Vito Servedio3, and Clemens Laubschat1 — 1Institut für Festkörperphysik, TU Dresden, D-01062 Dresden, Germany — 2Donostia International Physics Center, E-20018 Donostia/San Sebastian, Spain — 3Sezione INFM and Dip. di Fisica, Università “La Sapienza”, P. le A. Moro 2, I-00185 Roma, Italy
Valence-band photoemission spectra of close-packed surfaces of the divalent alkali-earth metals Be and Mg reveal huge peaks due to Shockley surface states with a free-electron like dispersion parallel to the surface. Similar states have been observed for close-packed surfaces of the noble metals Cu, Ag, Au, and the trivalent metal Al. Surprisingly, for the divalent metals Ca, Sr, Eu, and Yb as well as for all trivalent rare-earth metals such Shockley states are missing. Instead, rare-earth metals exhibit a d-like Tamm state that reveals almost no dispersion. On the basis of band-structure calculations, we show that this different behavior is caused by the d bands that convert the Shockley-inverted energy gaps at the close-packed surfaces of Be, Mg, Cu, Ag, Au, and Al into conventional gaps in the latter group of metals.
Supported by DFG, project La 655/7-2 and SFB 463, TP B4.