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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.53: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

Optical Excitations of the Spin-Ladder Sr_14−xCa_xCu₂₄O₄₁ from FIR to UV — •C. Hilgers¹, M. Grüninger¹, M. Reuther¹, U. Ammerahl², P. Ribeiro³, B. Büchner³, and A. Revcolevschi² — ¹II. Physikalisches Institut, Universität zu Köln — ²Laboratoire de Physico-Chimie de L’Etat Solide, Université Paris-Sud, France — ³IFW Dresden

We present low-temperature optical conductivity data of the hole-doped spin-ladder compound Sr_14−xCa_xCu₂₄O₄₁ between 10 meV and 6 eV for x = 0, 5, and 8. The investigation aims at the understanding of the electronic structure, charge carrier distribution and low-temperature anomalies in the phonon excitation spectra. The optical conductivity along the rung and leg directions was derived by analyzing a combination of ellipsometry and reflectivity data. The temperature and doping dependence of the charge-transfer excitations is investigated with focus on excitonic effects. Moreover, the transfer of spectral weight from low to high energy is studied as a function of temperature.