Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.39: Poster

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

Anisotropic thermal transport in one-dimensional spin systems — •K. Kordonis¹, T. Lorenz¹, A. Freimuth¹, Y. Ueda², M. Isobe², A. Vasil’ev³, and S. Cheong⁴ — ¹II. Phys. Inst., Universität zu Köln — ²Inst. Sol. St. Phys., University of Tokyo — ³Low Temp. Phys. Dep., Moscow State University — ⁴Dep. of Phys. & Astron., Rutgers University

One-dimensional spin systems show unusual and rich physical properties. Of particular interest are the dynamics of magnetic excitations and their coupling to the lattice. A valuable tool for their study is provided by measurements of the thermal conductivity κ. We present measurements of κ of the spin-ladder system α-NaV₂O₅, of the spin-chain systems β-Na_0.33V₂O₅, LiV₂O₅ and the Haldane system Y₂BaNiO₅. A double-peak structure of κ versus T is obtained in both sodium vanadates along and perpedicular to the magnetic directions. The origin of these double peaks is ambiguous yet, but the isotropic behavior of κ concerning different lattice directions is evidence for a phononic thermal conductivity. The minimum of κ can be explained by damping close to the transition temperature. In LiV₂O₅, κ shows only one low-temperature maximum along and perpedicular to the chains. Accordingly, κ of the vanadates is purely phononic. In contrast, κ of Y₂BaNiO₅ behaves strongly anisotropic; a double-peak of κ versus T is obtained only along the spin chains. This is a clear evidence for an additional magnetic contribution to the thermal conductivity of the Haldane system.

supported by the DFG through SFB 608