Temporal dynamics of excitonic states with nonlinear electron-vibrational coupling

A straightforward extension to the stochastic time-dependent variational approach allows the introduction of higher-order interaction effects to the Hamiltonian of an electronic-vibrational system. This is done using an Ansatz for the global wavefunction, describing vibrational wavepackets as squeezed coherent states (a generalized version of Davydov Ansatz). The approach allows quantum dynamics simulation and simulation of spectroscopic signals on anharmonic molecular potential surfaces. We calculate electronic and vibrational dynamics for a number of model systems, showing some results attributed to nonlinearities in spectroscopy experiments (such as breaking of mirror symmetry between absorption and fluorescence signals) and analyzing the influence of nonlinear effects on electronic energy transfer in multi-site aggregates. Published by AIP Publishing.