  We investigate the heat transport in a nonequilibrium spin-boson model, where
a two level system bridging two harmonic reservoirs at different temperatures,
by employing a unitary transformation along with a resolvent operator expansion
technique. Analytical expressions of the heat current and the thermal
conductance of this model are obtained. Compared with the performances of other
methods, namely, the nonequilibrium Green's function method and the equation of
motion formulation, our approach provides a reasonable description of heat
transfer properties of the nonequilibrium spin-boson model for the
weak-coupling region at low temperature.
