We investigate theoretically how energy dissipates and migrates from one place to another in complex and bi-dimensional molecular aggregates. In this context, a key role is played by resonance electronic energy transfer (RET) processes [1] through which an excitation initially stored onto a donor molecule (D) can be transferred to an acceptor molecule (A). Despite its long history, the mechanism of RET is still not completely understood and is the object of intense research activities and debates [2].
In this presentation, we address the question of how to describe collective and non-equilibrium effects in RET processes after all the donor molecules have been excited by a pump laser (see Fig). We predict that, due to the dimensionality of the network, the effective rate of RET scales as ^{\alpha}, with the average distance between individual excited donors and their nearest-neighbor acceptor molecules, and \alpha \in [-6, -2] an exponent depending on the spatial distribution of molecular pairs in the 2D sample [3]. We show departures from this mean-field description arising from fluctuations and spatial correlations between several molecules involved in the RET process.
The relevance of such stochastic approaches is further investigated in order to capture the essential features of more recent experiments related to energy transfer in optical cavities [4]. In the latter case, we show as preliminary results that the interaction between pairs of molecules inside cavity can be highly modified with consequences on the kinetics of RET processes inside cavity [5].

References:
[1] T. Förster. “Transfer mechanisms of electronic excitation energy” (1960).

[2] S. Jang, M. D. Newton, and R. J. Silbey. Phys. Rev. Lett. 92, 218301 (2004).

[3] R. Avriller, A. Marché, and G. Jonusauskas, Phys. Rev. B 108, 205419 (2023).

[4] X. Zhong et al., Angewandte Chemie International Edition, 56(31), 9034-9038 (2017).

[5] K. Wu, D. Hagenmüller et R. Avriller, in preparation (2026).