Photon-photon correlations in "two-color" dimer molecules

We compute second-order photon-photon correlation functions for light emission from a heterodimer molecule in a thermal bath, which reveal quantum effects in energy transfer processes. Such correlations are experimentally measurable observables that enable the dynamic probing of quantum effects. Specificially, we identify photon bunching and anti-bunching, corresponding to classical and quantum behaviour. We consider light emission from a "two-color" dimer consisting of "blue" and "red" monomer units. When continuously driven with a laser tuned close to the "blue" monomer transition, we compute the photon-photon correlations for emission at the "red" monomer frequency, to identify signatures of quantum signatures arising from the energy transfer in the dimer molecule in its photon emission. In addition to one- and two-colour photon correlation functions, photon-phonon cross-correlation functions can also provide observable signatures of vibrational interactions with the environment.