The Rise and Current Status of Polaritonic Photochemistry and Photophysics

Abstract

The interaction between molecular electronic transitions and electromagnetic fields can be enlarged to the point where distinct hybrid light–matter states, polaritons, emerge. The photonic contribution to these states results in increased complexity as well as an opening to modify the photophysics and photochemistry beyond what normally can be seen in organic molecules. It is today evident that polaritons offer opportunities for molecular photochemistry and photophysics, which has caused an ever-rising interest in the field. Focusing on the experimental landmarks, this review takes its reader from the advent of the field of polaritonic chemistry, over the split into polariton chemistry and photochemistry, to present day status within polaritonic photochemistry and photophysics. To introduce the field, the review starts with a general description of light–matter interactions, how to enhance these, and what characterizes the coupling strength. Then the photochemistry and photophysics of strongly coupled systems using Fabry–Perot and plasmonic cavities are described. This is followed by a description of room-temperature Bose–Einstein condensation/polariton lasing in polaritonic systems. The review ends with a discussion on the benefits, limitations, and future developments of strong exciton–photon coupling using organic molecules.

Ab Initio Vibro-Polaritonic Spectra in Strongly Coupled Cavity-Molecule Systems

“…Strong light–matter coupling between a molecular system and the electromagnetic field of an optical cavity offers new possibilities to modify chemical reactivity and selectivity, as demonstrated in recent experiments. − A particularly intriguing but not yet fully understood situation occurs when a cavity mode is strongly coupled to molecular vibrations, called vibrational-strong coupling (VSC). − For VSC the rate constants of ground state reactions can be modified even without external driving, i.e., without explicitly adding photons to the cavity. Probably one of the most striking features observed in such experiments is the change of the vibrational spectra due to the formation of molecular vibrational polaritons, hybrid states that involve both cavity modes and vibrational modes of molecules.…”

Collective Strong Coupling Modifies Aggregation and Solvation

“…The coherent interaction of molecules with confined optical modes leads to hybrid light–matter states called polaritons. − In the strong coupling regime, usually achieved by coupling several molecules to the optical cavity, experiments show significant modifications of chemical properties. − As a result of their delocalized nature, polaritons in quantum optics are studied from a collective perspective where the molecules are modeled as few-level systems that indirectly interact solely through the photon field. − However, chemistry is governed by local interactions, and the molecular complexity requires refined chemical methods to analyze processes like reactions. The behavior of molecules is, hence, susceptible to their immediate surroundings.…”

Variational Lang–Firsov Approach Plus Møller–Plesset Perturbation Theory with Applications to Ab Initio Polariton Chemistry

“…A polaron is a quasiparticle consisting of an electron and its surrounding lattice deformation (phonons), whereas a polariton is a quasiparticle resulting from the strong coupling between matter excitations, such as excitons and photons. Historically, the polaron problem has been a classic topic in condensed matter physics and plays a key role in various important phenomena, including charge transport (mobility), magnetism, and superconductivity. , Recently, cavity-mediated chemical reactions have attracted renewed attention to polaritons, where experimental claims have been put forward that chemical reaction rates and pathways can be manipulated by the formation of polaritons in an optical cavity, − potentially providing a new dimension for fine control of chemical processes. ,− …”