Photoprotecting Uracil by Coupling with Lossy Nanocavities

Abstract

We analyze how the photorelaxation dynamics of a molecule can be controlled by modifying its electromagnetic environment using a nanocavity mode. In particular, we consider the photorelaxation of the RNA nucleobase uracil, which is the natural mechanism to prevent photodamage. In our theoretical work, we identify the operative conditions in which strong coupling with the cavity mode can open an efficient photoprotective channel, resulting in a relaxation dynamics twice as fast as the natural one. We rely on a state-of-the-art chemically detailed molecular model and a non-Hermitian Hamiltonian propagation approach to perform full-quantum simulations of the system dissipative dynamics. By focusing on the photon decay, our analysis unveils the active role played by cavity-induced dissipative processes in modifying chemical reaction rates, in the context of molecular polaritonics. Remarkably, we find that the photorelaxation efficiency is maximized when an optimal trade-off between light–matter coupling strength and photon decay rate is satisfied. This result is in contrast with the common intuition that increasing the quality factor of nanocavities and plasmonic devices improves their performance. Finally, we use a detailed model of a metal nanoparticle to show that the speedup of the uracil relaxation could be observed via coupling with a nanosphere pseudomode, without requiring the implementation of complex nanophotonic structures.

Photoisomerization Efficiency of a Solar Thermal Fuel in the Strong Coupling Regime

“…This reduction is increased when the cavity resonance is shifted to lower energies, highlighting the importance of the photon decay of the cavity mode for excited state reactions in the strong coupling regime. [ 11,25 ] Furthermore, we show that the back reaction is not affected by the strong coupling regime since it occurs on the ground state potential energy surface. The system therefore has a red‐shifted onset of absorption and at the same time a retained back reaction.…”

Simulating photodissociation reactions in bad cavities with the Lindblad equation

“…As a general remark, to minimize computational cost, the Lindblad master equation can be reduced to a non-Hermitian Schrodinger equation employing an absorbing potential, given the following three conditions: The Hamiltonian does not couple any state in the subspace to other states that are not in the subspace, the initial state projected onto that subspace is a pure state, and the subspace is not the recipient of decaying states. This motivates the method in previous studies, 19 – 21 but in this study, these conditions only apply to the doubly excited subspace (see Fig. 2 for definitions of subspaces).…”

“…It is worth noting that the stability optimum is at the border of the strong coupling regime, which has also been found in other studies. 21 This suggests that it may be an interplay of strong coupling and cavity cooling, which is required to explain polaritonic chemistry experiments.…”

“…However, not all parameters describing the cavity structure have gained equal attention. Effects arising from a finite lifetime for field excitations, also known as the cavity Q-factor or photon decay rate, have only recently been the main focus in a few ground-breaking studies, 19 – 21 and dissipative effects, in general, have been described as a challenge for computational methods 1 .…”

“…Recent publications 19 – 21 , 29 , 30 on cavity decay do not deal directly with the Lindblad equation formalism; instead, the underlying formalism is a non-Hermitian evolution of a pure state, which is shown to be appropriate for both relaxation dynamics 19 , 21 and isomerization. 20 However, for general applications, the method omits some phenomenological processes, such as decoherence and time evolution of statistically mixed states, and the impact of this exclusion depends on the type of system and is observable under investigation.…”