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Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.39: Poster

Saturday, March 5, 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. Cheong41II. 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-Na0.33V2O5, 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.

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