The optical excitation of molecules can induce non-trivial forces, that are connected to a wide range of phenomena, including chemical bond dissociation, and intricate biological processes that underpin vision. The standard first-principles description of optical excitations entails solution of the computationally demanding electronic Bethe-Salpeter equation (BSE). However, when studying non-covalent interactions in large-scale systems, more efficient methods are desirable.
Here we introduced an effective approach based on coupled quantum Drude oscillators (cQDO). The cQDO Hamiltonian yields semi-quantitative agreement with BSE calculations, revealing that both attractive and repulsive optical van der Waals (vdW) forces can be induced by light.
Optical-vdW interactions dominate over vdW dispersion in the long-distance regime due to their ultra-slow decay, showing a complexity that grows with system size. Evidence of highly non-local forces in the human formaldehyde dehydrogenase 1MC5 protein suggests the ability to selectively activate collective molecular vibrations by photoabsorption, compatibly with recent experimental observation of phonon condensation induced by absorbed light.
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