Davydov Ansatz as an efficient tool for the simulation of nonlinear optical response of molecular aggregates

We have developed a variational approach to the description of four-wave-mixing signals of molecular aggregates, in which the third-order response functions are evaluated in terms of the Davydov Ansatze. Our theory treats both singly and doubly excited excitonic states, handling the contributions due to stimulated emission, ground state bleach, and excited state absorption. As an illustration, we simulate a series of optical two-dimensional spectra of model J-aggregates. Our approach may become suitable for the computation of femtosecond optical four-wave-mixing signals of molecular aggregates with intermediate-to-strong exciton-phonon and exciton-exciton coupling strengths. (C)d 2015 AIP Publishing LLC.