Many chemical methods have been developed to favor a particular product in transformations of compounds that have two or more reactive sites. We explored a different approach to site selectivity using vibrational strong coupling (VSC) between a reactant and the vacuum field of a microfluidic optical cavity. Specifically, we studied the reactivity of a compound bearing two possible silyl bond cleavage sites—Si–C and Si–O, respectively—as a function of VSC of three distinct vibrational modes in the dark. The results show that VSC can indeed tilt the reactivity landscape to favor one product over the other. Thermodynamic parameters reveal the presence of a large activation barrier and substantial changes to the activation entropy, confirming the modified chemical landscape under strong coupling.

The ground‐state deprotection of a simple alkynylsilane is studied under vibrational strong coupling to the zero‐point fluctuations, or vacuum electromagnetic field, of a resonant IR microfluidic cavity. The reaction rate decreased by a factor of up to 5.5 when the Si−C vibrational stretching modes of the reactant were strongly coupled. The relative change in the reaction rate under strong coupling depends on the Rabi splitting energy. Product analysis by GC‐MS confirmed the kinetic results. Temperature dependence shows that the activation enthalpy and entropy change significantly, suggesting that the transition state is modified from an associative to a dissociative type. These findings show that vibrational strong coupling provides a powerful approach for modifying and controlling chemical landscapes and for understanding reaction mechanisms.

Light–matter strong coupling allows for the possibility of entangling the wave functions of different molecules through the light field. We hereby present direct evidence of non‐radiative energy transfer well beyond the Förster limit for spatially separated donor and acceptor cyanine dyes strongly coupled to a cavity. The transient dynamics and the static spectra show an energy transfer efficiency approaching 37 % for donor–acceptor distances ≥100 nm. In such systems, the energy transfer process becomes independent of distance as long as the coupling strength is maintained. This is consistent with the entangled and delocalized nature of the polaritonic states.

：Room temperature strong coupling of WS 2 monolayer exciton transitions to metallic Fabry-Perot and plasmonic optical cavities is demonstrated. A Rabi splitting of 101 meV is observed for the Fabry-Perot cavity, more than double those reported to date in other 2D materials. The enhanced magnitude and visibility of WS 2 monolayer strong coupling is attributed to the larger absorption coefficient, the narrower linewidth of the A exciton transition, and greater spin-orbit coupling. For WS 2 coupled to plasmonic arrays, the Rabi splitting still reaches 60 meV despite the less favorable coupling conditions, and displays interesting photoluminescence features. The unambiguous signature of WS 2 monolayer strong coupling in easily fabricated metallic resonators at room temperature suggests many possibilities for combining light-matter hybridization with spin and valleytronics. induces the splitting of the excitonic transition by ca. 150 meV such that both the so-called A and B exciton transitions (see Figure 1b) can simultaneously interact with cavity modes complicating the studies of such systems. 27 The WS 2 monolayer has the advantage that it presents a much sharper isolated absorption band as can be seen in Figure 1b. In addition it displays an intense photoluminescence (PL) peak at 2.016 eV (Figure 1c). Hence WS 2 constitutes a natural choice for light-matter strong coupling. In this letter we demonstrate that by coupling WS 2 monolayers to metallic resonators, the magnitude and visibility of light-monolayer TMD strong coupling at room temperature is substantially enhanced with a Rabi splitting of 101 meV in Fabry-Perot cavities and 60 meV on plasmonic arrays. The energy-momentum dispersion properties of the monolayer WS 2 excitonpolaritons are explored by transmission, reflection and photoluminescence (PL) spectroscopy. In particular Rabi splittings in TE and TM dispersion curves give rise to unusual PL behavior. The results are discussed in terms of the potential of coherent light-matter interactions using WS 2 monolayers.To ensure high quality samples and to avoid environmental contamination, the TMD monolayers were exfoliated from bulk single crystals and then dry-transferred onto substrates as the holes possibly due to two factors: firstly, the plasmonic field has a maximum above the holes, enhancing the photonic mode density at this point, thereby increasing the excitonic radiative rate, 32 and secondly the increased dielectric screening where the monolayer is suspended over the hole rather than in Van der Waals contact with the substrate could enhance the emission. 10Angle-resolved transmission spectra of the FP cavity with WS 2 monolayer are shown in Figure 3a for TE polarization. The progressive dispersion of the cavity mode through the energy of the A exciton is accompanied by a clear anti-crossing, which is mapped out in terms of spectral maxima in Figure 3b. After fitting the energy of the two peaks as a function of in-plane momentum k // using the coupled oscillator model (described in the Met...

From the high vibrational dipolar strength offered by molecular liquids, we demonstrate that a molecular vibration can be ultrastrongly coupled to multiple IR cavity modes, with Rabi splittings reaching 24% of the vibration frequencies. As a proof of the ultrastrong coupling regime, our experimental data unambiguously reveal the contributions to the polaritonic dynamics coming from the antiresonant terms in the interaction energy and from the dipolar self-energy of the molecular vibrations themselves. In particular, we measure the opening of a genuine vibrational polaritonic band gap of ca. 60 meV. We also demonstrate that the multimode splitting effect defines a whole vibrational ladder of heavy polaritonic states perfectly resolved. These findings reveal the broad possibilities in the vibrational ultrastrong coupling regime which impact both the optical and the molecular properties of such coupled systems, in particular, in the context of mode-selective chemistry.

We present direct evidence of enhanced non-radiative energy transfer between two J-aggregated cyanine dyes strongly coupled to the vacuum field of a cavity. Excitation spectroscopy and femtosecond pump-probe measurements show that the energy transfer is highly efficient when both the donor and acceptor form light-matter hybrid states with the vacuum field. The rate of energy transfer is increased by a factor of seven under those conditions as compared to the normal situation outside the cavity, with a corresponding effect on the energy transfer efficiency. The delocalized hybrid states connect the donor and acceptor molecules and clearly play the role of a bridge to enhance the rate of energy transfer. This finding has fundamental implications for coherent energy transport and light-energy harvesting.

Vibrational strong coupling (VSC) has recently emerged as ac ompletely new tool for influencing chemical reactivity.I th arnesses electromagnetic vacuum fluctuations through the creation of hybrid states of light and matter,called polaritonic states,i na no ptical cavity resonant to am olecular absorption band. Here,weinvestigate the effect of vibrational strong coupling of water on the enzymatic activity of pepsin, where aw ater molecule is directly involved in the enzymes chemical mechanism. We observe an approximately 4.5-fold decrease of the apparent second-order rate constant k cat /K m when coupling the water stretching vibration, whereas no effect was detected for the strong coupling of the bending vibration. The possibility of modifying enzymatic activity by coupling water demonstrates the potential of VSC as anew tool to study biochemical reactivity.Vibrational strong coupling entails the formation of hybrid light-matter states,o rp olaritonic states,b yp lacing am olecular species in ap hotonic cavity resonant to one of its vibrational absorption bands under the right conditions ( Figure 1A). [1][2][3][4][5] Ar esonant cavity is as tructure which confines light spatially at well-defined frequencies,f or example,t wo parallel mirrors facing each other form aFabry-Perot cavity (Figure 1Band Supporting Information, Figure 1. Vibration strong coupling and pepsin. A) Schematic outline of strong light-matter interaction with molecular vibrations.I nanon resonancec avity where " hw vibr = " hw cavity ,the ground and first excited state of avibration will combine with the photon numbers tate of the photonic cavity to produce two new polaritons tates, P + and PÀ, separated by the vacuum Rabi splitting " hW R .B )Schematic drawing of the microfluidic cavities used here for studying pepsin-mediated peptide hydrolysis under VSC of the water mid-infrared bands. C) Mechanistic model of peptide bond cleavage in the active site of pepsin based on ref. [8].

We report here a study of light-matter strong coupling involving three molecules with very different photo-physical properties. In particular we analyze their emission properties and show that the excitation spectra are very different from the static absorption of the coupled systems. Furthermore we report the emission quantum yields and excited state lifetimes, which are self-consistent. The above results raise a number of fundamental questions that are discussed and these demonstrate the need for further experiments and theoretical studies.