Theory of Open Quantum Systems as Applied to Spin Relaxation in Solids
  We employ the method of the theory of open quantum systems to analyze spin relaxation and decoherence in semiconductors in the presence of a magnetic field. We derive a set of Bloch equations for electron spin with a fully microscopic determination of longitudinal and transverse relaxation times. Electron scattering from optical and acoustic phonons and random impurities is taken into account. We obtain explicit expressions for the spin relaxation times in terms of material constants and coupling strengths, exhibiting formal agreement with earlier treatments in the zero magnetic field limit with microscopic specification of their phenomenological parameters. 
Vadim I. Puller, Lev G. Mourokh, Norman J.M. Horing and Anatoly Yu.   Smirnov