# An exactly solvable model for coherent and incoherent exciton motion

H. Haken and G. Strobl. Zeitschrift für Physik 262, 135-148 (1973)

### Abstract

We treat the motion of a Frenkel exciton using a Hamiltonian which comprises a completely coherent part and a fluctuating part which describes both fluctuations of the energy of a localized exciton and fluctuations of the transition matrix elements between different lattice sites. Under the assumption that the fluctuating forces are Markoffian and Gaussian we derive exactly a density matrix equation which can be solved by a Green's function method.