Non-adiabatic transition in spin-boson model and generalization of the Landau–Zener formula

Non-adiabatic transitions are studied in a spin-boson model with multiple scattering points. In order to generalize the Landau–Zener formula, which describes the case of a single scattering point, we define an “effective gap” for a set of scattering points. The generalized formula agrees very well with numerical results of the non-adiabatic dynamics, which we obtained by a direct numerical method. This will make the Landau–Zener formula yet more useful in analyzing experimental data of magnetic-moment inversion.