EFFECT OF A SITE-DEPENDENT NONLINEAR ELECTRON-PHONON COUPLING ON THE CHARACTER OF COHERENT AND DISSIPATIVE DYNAMICS OF A MOLECULAR DIMER

The dynamics of particle or quasiparticle motion in a molecular adiabatic dimer with site-dependent nonlinear polaronic coupling has been investigated in both coherent and dissipative regimes. An analysis of equations of motion for the Bloch-vector components has been performed. Our results show that the character of coherent dynamics is strongly influenced by nonlinear coupling. Exact conditions for self-trapping and transfer oscillations have been derived. It was shown that dissipative dynamics, particularly the character of the steady state, is determined by the condition of detailed balance in accordance with thermodynamics. For a degenerate molecular dimer it was shown that, irrespective of a strong decrease of the energy of a site due to strong nonlinear polaronic coupling, the symmetry breaking in the asymptotic distribution does not occur.