We develop a theoretical model for transverse dynamics of a single electron
spin interacting with a nuclear spin bath. The approach allows a simple
diagrammatic representation and analytical expressions of different nuclear
spin excitation processes contributing to electron spin decoherence and
dynamical phase fluctuations. It accounts for nuclear spin dynamics beyond
conventional pair correlation models. As an illustration of the theory, we
evaluated the coherence dynamics of a P donor electron spin in a Si crystal.Comment: 37 pages, 13 figure