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TT: Tiefe Temperaturen

TT 30: Postersitzung IV: Kritische Ph
änomene, Quantenstörstellen, niederdimensionale Systeme

TT 30.12: Poster

Thursday, March 11, 2004, 14:30–19:00, Poster A

Obtaining optical constants for resonant soft x-ray scattering — •J. Schlappa¹, C. Schüßler-Langeheine¹, Z. Hu¹, M. W. Haverkort¹, E. Schierle², H. Ott², E. Weschke², G. Kaindl², P. Abbamonte³, M. Huijben⁴, G. Rijnders⁴, D. H. A. Blank⁴, A. Tanaka⁵, and L. H. Tjeng¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²Institut für Experimentalphysik, Freie Universität Berlin — ³NSLS, Brookhaven National Laboratory, USA — ⁴Faculty of Science and Technology, University of Twente, Enschede, Netherlands — ⁵ADSM, Hiroshima University, Japan

The new technique of resonant soft x-ray scattering at the transition metal L_2,3 and lanthanide M_4,5 absorption edges is uniquely suited to study order phenomena like spin, charge and orbital order in correlated solids. A quantitative data analysis, however, requires the precise determination of optical constants across the resonance. While these constants are quite well known for energies far off resonance, reliable data on resonance, where the index of refraction shows a strong energy dependence, are missing. As a model system, we studied different surfaces of SrTiO₃ at the Ti L_2,3 resonance and obtained the optical parameters either indirectly from a Kramers-Kronig transform of the absorption signal or directly by measuring reflectivity and from that determined the critical angle of total reflection. These results will be compared to theoretical values. We demonstrate how much a proper data interpretation depends on the precise knowledge of optical constants and discuss the suitability and accuracy of either exprimental techniqe for their determination.