Diffusion coefficient for disordered systems with coupled coherent and incoherent transport in one dimension

We present a calculation of the diffusion coefficient from a Hamiltonian fo r coupled coherent and incoherent transport with site-diagonal and off-diag onal stochastic fluctuations, which is not restricted to the usual white no ise expression for the correlation between the fluctuating variables. Our r esult is applicable to any specific correlation and allows for long correla tion times. We give examples for both monotonically decreasing and oscillat ing correlations. In the case of an exponential decay of the correlations t he diffusion coefficient can be expressed by complete elliptic integrals. ( C) 2000 American Institute of Physics. [S0021- 9606(00)51438-X].