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Magnon Heat Transport in (Sr,La)14Cu24O41

C. Hess, C. Baumannn, U. Ammerahl, B. Büchner, F. Heidrich-Meisner, W. Brenig, A. Revcolevschi

cond-matarXiv:cond-mat/0105407

Abstract

We have measured the thermal heat conductivity kappa of the compounds Sr14Cu24O41 and Ca9La5Cu24O41 containing doped and undoped spin ladders, respectively. We find a huge anisotropy of both, the size and the temperature dependence of kappa which we interpret in terms of a very large heat conductivity due to the magnetic excitations of the one-dimensional spin ladders. This magnon heat conductivity decreases with increasing hole doping of the ladders. The magnon heat transport is analyzed theoretically using a simple kinetic model. From this analysis we determine the spin gap and the temperature dependent mean free path of the magnons which ranges by several thousand angstroms at low temperature. The relevance of several scattering channels for the magnon transport is discussed.

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