Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 27: Superconductivity: Cuprate Superconductors

TT 27.4: Vortrag

Mittwoch, 28. März 2012, 12:15–12:30, H 2053

Peculiar temperature and momentum dependence in the spin ladder systems Ca_xSr_14−xCu₂₄O₄₁ — •Friedrich Roth¹, Christian Hess¹, Udo Ammerahl², Alexandre Revcolevschi², Bernd Büchner¹, and Martin Knupfer¹ — ¹IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany — ²Laboratoire de Physico-Chimie de l’État Solide, Université Paris-Sud, 91405 Orsay, France

Electron energy-loss spectroscopy has been used to investigate the loss-function of the single crystalline two - leg ladder system Ca_xSr_14−xCu₂₄O₄₁ with various compositions. We find a strong anisotropy of the loss function for momentum transfers along the a and c - crystallographic axis, and a remarkable linear plasmon dispersion for a momentum transfer parallel to the legs of the ladders. The investigated spectral features are attributed to localized and delocalized charge-transfer excitations and the charge carrier plasmon. The charge carrier plasmon position and dispersion in the long wave-length limit agree well with expectations based upon the band structure of the two-leg ladder, while the observed quasi-linear plasmon dispersion might be related to the peculiar properties of underdoped cuprates in general. Furthermore, a remarkable temperature dependence of the plasmon was observed.