Regensburg 2000 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 22: Postersitzung III: Supraleitende Anwendungen (1-4) Massive HTSL, Bandleiter, Filme (5-26), Transport in HTSL (27-30), Elektronenstruktur in Supraleitern (31-43), Borkarbide (44-50), Quantenphasen- und Metall-Isolator-Überg
änge (51-69)

TT 22.51: Poster

Donnerstag, 30. März 2000, 14:00–17:30, A

Effect of Ca- and Zn-Substitution on the charge ordering and gap formation in (Sr,Ca)₁₄(Cu,Zn)₂₄O₄₁ — •M. Grove¹, P. Lemmens¹, A. Ionescu¹, P.H.M. van Loosdrecht¹, G. Güntherodt¹, U. Ammerahl², B. Büchner², R. Gross², A. Revcolevschi³, and J. Akimitsu⁴ — ¹2. Physikalisches Institut, RWTH Aachen, 52056 Aachen — ²2. Physikalisches Institut, Universität zu Köln, 50937 Köln — ³Universität Paris-Süd, 91405, Orsay, Frankreich — ⁴Aoyama Gakuin University, Tokyo, Japan

Raman scattering studies on single crystals of Sr_14−xCa_xCu_24−yZn_yO₄₁ (x=0, 2, 5, 12; y=0, 0.5), which contain simple edge sharing CuO₂ chains and two-leg Cu₂O₃ ladders are reported. A spin gap formation in the chain subcell is observed as a drop of scattering intensity, with Δ_chain=140±10 K, while the gap in the ladder subcell shows up as an additional shoulder, corresponding to Δ_ladder=350±20 K. In addition, phonon anomalies are observed and attributed to charge ordering in the chain subcell. Substitution studies point to a strong sensitivity of the gap in the chain subcell on Ca-content. This is due to a crossover from long range to short range charge ordering with increasing x. In Zn-substituted samples a similar suppression of long range charge order is observed and attributed to disorder. In contrast to these effects the gap in the ladder subcell is not influenced by Ca-substitution.
Work supported by DFG through SFB 341.