Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 33: New materials

HL 33.1: Talk

Wednesday, March 28, 2007, 16:45–17:00, H15

Study of the Ba giant dipole resonance in Ba₈Si₄₆ with non-resonant inelastic x-ray scattering — •Sternemann Henning¹, Sternemann Christian¹, Tse John S.², Desgreniers Serge³, Vankó György⁴, Schacht Andreas¹, Soininen Juha Aleksi⁵, and Tolan Metin¹ — ¹Dept. Phys. / DELTA, University of Dortmund, D-44221 Dortmund — ²Dept. Phys. & Engn. Phys., University of Saskatchewan, Canada — ³Dept. Phys., University of Ottawa, Canada — ⁴ESRF, Grenoble, France — ⁵Div. X-ray Physics, Dept. Physical Sciences, University of Helsinki, Finland

Atomic Ba shows a giant dipole resonance arising from collective 4d electron motion above the energetic threshold of the N_IV,V edges. We will present the first experimental observation of the Ba resonance in the complex silicon clathrate network of Ba₈Si₄₆. The measurements were done at different momentum transfers using non-resonant inelastic x-ray scattering. The giant resonance spectra were modeled within the time-dependent local density approximation using a real-space multiple-scattering approach. The resulting spectra show very good agreement with the experiment. Separate calculations for Ba@Si₂₀ and Ba@Si₂₄ demonstrate the sensitivity of the resonance concerning the local environment of the Ba atom. Thus, a combined study of absorption edges and the fine-structure of the giant resonance by means of non-resonant inelastic x-ray scattering yields the possibility to study electronic and structural changes in pressure-induced phase transitions of the clathrate simultanously. The experimental setup for such studies will also be presented.