Dynamics of an impurity spin coupled to a spin-boson dissipative system

The authors study the dynamics of an impurity spin coupled to a spin-boson dissipative system. They calculate the transverse correlation function of the impurity spin and compare the result with that obtained from an equivalent stochastic model. A phenomenological rate parameter in the stochastic model is represented in terms of microscopically obtained quantities. The authors also calculate the NMR lineshapes for various temperatures which are relevant in the context of a particular physical realization of the model. Motional narrowing of lines is observed at high temperatures