Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 27: CE: Poster Session
TT 27.69: Poster
Wednesday, March 24, 2010, 14:00–18:00, Poster D1
Spinon localization in the heat transport of the spin-1/2 ladder compound (C5H12N)2CuBr4 — •Gerhard Kolland1, Jens Rohrkamp1, Beni Thielemann2, Henrik M. Ronnow3, Christian Rüegg4, Karl Krämer5, John A. Mydosh1, Alexandr V. Sologubenko1, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln, Germany — 2Lab. for Neutron Scattering, ETH Zürich & PSI Villigen, Switzerland — 3Lab. for Quantum Magnetism, EPFL, Switzerland — 4London Centre for Nanotech. and Dep. of Phys. and Astron., University College London, UK — 5Dep. of Chem. and Biochem., University of Bern, Switzerland
Piperidium copper bromide (C5H12N)2CuBr4 is a two-leg spin-1/2 ladder system with comparatively weak antiferromagnetic exchange couplings along the legs and the rungs. Hence, this system has two experimentally accessible quantum phase transitions; from a gapped spin-singlet state to a gappless Luttinger-liquid state at Hc1≃ 7 T and from this state to a fully polarized state at Hc2≃ 14 T. Here, we present experiments on the magnetic field-dependent thermal transport. The thermal conductivity is only weakly affected by the field-induced transitions at Hc1/c2, suggesting the absence of a direct contribution of the spin excitations to the heat transport. We observe, however, that the thermal conductivity is suppressed by the magnetic field deeply within the Luttinger-liquid state. These surprising observations are discussed in terms of localization of spinons within finite ladder segments and spinon-phonon umklapp scattering of the predominantly phononic heat transport.Supported by the DFG through SFB 608.