Many-body Interactions in Ultrafast Spectroscopy

Diego Florio; Alessandro Baserga; Sofia Bertuetti; Federico Visentin; Adar Levi; Uri Banin; Giulio Cerullo; Franco V. A. Camargo

arXiv · 2610.07213

Many-body Interactions in Ultrafast Spectroscopy

Diego Florio·Alessandro Baserga·Sofia Bertuetti·Federico Visentin·Adar Levi·Uri Banin·Giulio Cerullo·Franco V. A. Camargo

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Abstract

Nonlinear spectroscopy is widely used to probe ultrafast dynamics in matter. Signals of higher nonlinear orders encode valuable many-body dynamics but only recently have become individually retrievable. However, their physical interpretation in terms of double-sided Feynman diagrams is cumbersome and non-intuitive. Here, we establish an alternative framework that connects them to the underlying excitation conditions and many-body interactions. This approach predicts two classes of dynamic nonlinearities, due either to direct many-body interactions or to saturable kinetic channels. The method provides a direct physical interpretation of the retrieved signals, explaining their sign, magnitude, and dynamics. It also enables model-free reconstruction of the dynamics of a sub-ensemble of particles starting with a given number of excitons, which we demonstrate to be especially insightful. We validate the framework using colloidal CdSe/CdS core/shell quantum dots, which enable us to model nonlinearities of both classes in isolation and also combined.

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Diego Florio, Alessandro Baserga, Sofia Bertuetti, Federico Visentin, Adar Levi, Uri Banin, Giulio Cerullo, Franco V. A. Camargo. 2026-10-05. Many-body Interactions in Ultrafast Spectroscopy. https://arxiv.org/abs/2610.07213

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