Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique
TT 16.2: Poster
Samstag, 5. März 2005, 11:00–16:30, Poster TU C
Finite-frequency transport properties of dimerized and frustrated spin-1/2 chains — •Fabian Heidrich-Meisner, Andreas Honecker, and Wolfram Brenig — Technische Universität Braunschweig, Institut für Theoretische Physik, Mendelssohnstraße 3, 38106 Braunschweig
We present a numerical study of both spin and thermal transport in dimerized and
frustrated spin-1/2 chains at finite temperatures. Since both models are
nonintegrable, the Drude weights scale to zero in the thermodynamic limit [1].
We therefore focus on the behavior of the conductivities at finite
frequencies, studying the scaling with system size as well as the extrapolation
to the zero-frequency limit. Results for three examples are presented. First,
the dimerized chain is studied in the limit of weakly coupled dimers. In this case,
interactions of the elementary triplet excitations are weak, which allows us to
compute the life-times of the energy and the spin current analytically in a perturbative scheme within
a bond-boson operator representation. Second, we compare the conductivities of the
frustrated chain in the massless and the massive regime of this model. Finally,
we extract the zero-frequency thermal conductivity of the isotropic two-leg spin ladder
from the numerical data and suggest a comparison with experimental
results for La5Ca9Cu24O41 [2].
[1] F. Heidrich-Meisner et al., Phys. Rev. B 68, 134436 (2003).
[2] C. Hess et al., Phys. Rev. B 64, 184305 (2001).