Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.35: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

Optical studies on the two-leg ladder compounds Sr_14−xCa_xCu₂₄O₄₁ under pressure — •S. Frank¹, R. Klingeler², B. Büchner², and C. A. Kuntscher¹ — ¹1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany — ²Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, PF 27 01 16, 01171 Dresden, Germany

The low-dimensional quantum spin system Sr₁₄Cu₂₄O₄₁, composed of planes consisting of edge-sharing CuO₂ chains and planes of two-leg Cu₂O₃ ladders, has been studied extensively because of its interesting electronic and magnetic properties. Its electronic characteristics and the distribution of charges among the various structural entities are influenced by Ca-doping. The most interesting phenomenon in Sr₁₄Cu₂₄O₄₁ is a superconducting phase for high Ca-doping and under high pressure. Pressure-dependent resistivity measurements on Sr_2.5Ca_11.5Cu₂₄O₄₁ [1] suggest the occurrence of a dimensional crossover from one to two under pressure, and that the superconductivity in this system is essentially a 2D phenomenon.

We carried out polarization-dependent RT reflectivity measurements on Sr_14−xCa_xCu₂₄O₄₁ single crystals, with x=4 and 11.5, as a function of pressure (<20 GPa). The results are discussed in terms of changes in the charge dynamics along and perpendicular to the ladders and a possible pressure-induced dimensional crossover. Supported by the DFG, Emmy Noether-program.

[1] T. Nagata et al., Phys. Rev. Lett. 81, 1090 (1998).