Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 3: Spin-Systeme und itinerante Magnete
TT 3.6: Vortrag
Montag, 8. März 2004, 10:45–11:00, H18
Non-dissipative thermal transport and crossover phenomena in the gapped spin-1/2 XXZ chain — •Andreas Klümper1 and Kazumitsu Sakai2 — 1Universität Wuppertal, Theoretische Physik, Gauß-Straße 20 — 2Institute for solid state physics, University of Tokyo
We present exact results on the thermal conductivity of the one-dimensional spin-1/2 XXZ model in the gapless and the massive antiferromagnetic as well as ferromagnetic regimes. The thermal Drude weight is calculated by a lattice path integral formulation. Numerical results for wide ranges of temperature and anisotropy as well as analytical results in the low and high temperature limits are presented. At finite temperature, the thermal Drude weight is finite and hence there is non-dissipative thermal transport even in the massive regimes.
At low temperature, the thermal Drude weight behaves as Dth(T)∼ T in the gapless regime, and as Dth(T)∼ e−δ/T/√T in the gapped regimes where δ is the one-spinon/one-magnon excitation gap in the antiferromagnetic/ferromagnetic case. In the ferromagnetic regime we observe a crossover in the low-temperature behaviour of the ratio of the thermal Drude weight and the specific heat from Dth(T)/C(T)≃ T to Dth(T)/C(T)≃ T3/2e−β(δm−δs) when changing from Δ<5/3 to Δ>5/3 (δm and δs are the magnon and the spinon gap).