High temperature thermal conductivity of two-leg spin-1/2 ladders

Based on numerical simulations, a study of the high temperature, finite frequency, thermal conductivity kappa(omega) of spin-1/2 ladders is presented. The exact diagonalization and a novel Lanczos technique are employed. The conductivity spectra, analyzed as a function of rung coupling, point to a nondiverging dc limit but to an unconventional low frequency behavior. The results are discussed in perspective with recent experiments indicating a significant magnetic contribution to the energy transport in quasi-one-dimensional compounds.