Thermal transport in a spin-12Heisenberg chain coupled to a magnetic or nonmagnetic impurity

We explore the effect of a (non-)magnetic impurity on the thermal transport of the spin-$\frac{1}{2}$ Heisenberg chain model. This unique system allows to probe Kondo-type phenomena in a prototype strongly correlated system. Using numerical diagonalization techniques we study the scaling of the frequency dependent thermal conductivity with system size and host-impurity coupling strength as well as the dependence on temperature. We focus in particular on the analysis of ``cutting healing'' of weak links or a magnetic impurity by the host chain via Kondo-like screening as the temperature is lowered.