Absorption and photoluminescence in organic cavity QED

Herrera, Felipe; Spano, Frank C.

doi:10.1103/physreva.95.053867

Cited by 121 publications

(198 citation statements)

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“…properties for the two polaritonic states, a clear symmetry breaking between them is observed. Such symmetry breaking is known to occur for incoherent relaxation processes in such systems [7,27,28,44,51]. Interestingly, as seen by our measurements, this also exists in the short time-scale ellastic scattering processes.…”

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confidence: 76%

“…We note that in previous studies, the absorption of the two polaritonic levels was quantified by measuring the transmission and reflection spectra and then using A = 1 − T − R to infer the absorption spectrum [28,[42][43][44]. However, as our measurements indicate scattering from the polaritonic states cannot be neglected and therefore in order to obtain an accurate measure of the overall energy dissipated in the sample one needs to use the relation A = 1 − T − R − S. Unlike the resonant Rayleigh scattering from polaritonic states that has been observed in strongly coupled systems containing either inorganic semiconductors [45][46][47][48] or organic crystals [49] and associated to imperfections in the otherwise perfect structure, in our system, the scattering is inherent to the molecular system but modified by the collective nature of strong coupling.…”

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confidence: 99%

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Collective Rayleigh Scattering from Molecular Ensembles under Strong Coupling

Golombek

Balasubrahmaniyam

Kaeek

et al. 2020

J. Phys. Chem. Lett.

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Rayleigh scattering is usually considered to be the elastic scattering of photons from subwavelength physical objects, such as small particles or molecules. Here, we present the spectroscopic study of the scattering properties of molecules embedded in an optical cavity under strong coupling conditions, where the collective interaction between the molecules and the cavity gives rise to composite light-matter excitations known as cavity polaritons. We show that the polaritonic states exhibit strong resonant Rayleigh scattering, reaching ∼ 25% efficiency. Since the polaritonic wavefunctions in such systems are delocalized, our observations correspond to the collective scattering of each photon from a large ensemble of molecules.When quantum emitters are placed inside an optical cavity, their interaction with the quantized electromagnetic mode of the cavity may become large enough to overcome the incoherent processes taking place in the system [1]. This regime, which is known as strong light-matter coupling, has been extensively studied in hybrid molecular-photonic systems over the past decade, as it offers exciting possibilities for controlling the photophysical and chemical properties of molecules [2,3]. The coupling between an ensemble of molecules and an optical resonator is quantified by the vacuum Rabi frequency, which is roughly given byHere d is the transition dipole element of the molecules, is Planck's constant, ω c is the cavity resonance frequency, is the background dielectric constant inside the cavity, V c the cavity mode volume and N is the number of molecules inside the cavity. The √ N dependence of the coupling strength indicates that, under strong coupling conditions, the interaction between the molecules and the optical mode is collective. As a result, the eigenstates of the coupled system, known as cavity polaritons, represent a coherent superposition of a photon and a material excitation which is delocalized across a macroscopically large ensemble of molecules [1,4]. The collective nature of strong coupling in molecular systems is currently attracting considerable attention [5][6][7][8][9][10], as it gives rise to fascinating effects. These include, for instance, long-range spatial coherence [11][12][13], enhanced transport [14-18] and energy transfer [19][20][21], and even collective molecular reactivity [22][23][24][25].The progress in this evolving field is intimately linked to the extensive spectroscopic study of organic strongly coupled systems, which has gradually revealed the properties of the polari- * Corresponding author talschwartz@tau.ac.il

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confidence: 99%

Collective Rayleigh Scattering from Molecular Ensembles under Strong Coupling

Golombek

Balasubrahmaniyam

Kaeek

et al. 2020

J. Phys. Chem. Lett.

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“…These so-called "dark exciton states" [66] arise naturally from state classification by permutation symmetry in the Hilbert space of the Dicke model [67,68]. It has been shown originally within a quasi-particle approach for systems with macroscopic translational invariance [69], and later using a cavity QED approach [32,[70][71][72], that totally-symmetric and non-symmetric collective molecular states can strongly admix due to ever-present inhomogeneous broadening of molecular energy levels, inhomogeneities in the light-matter interaction energy across the medium, or any local coherent term such as intramolecular electron-vibration coupling (in the case of electronic strong coupling [72]). In general, the role of quasi-dark collective states in determining the rate of chemical reactions and also spectroscopic signals of vibrational polaritons is yet to be fully understood.…”

Section: Discussionmentioning

confidence: 99%

Multi-level quantum Rabi model for anharmonic vibrational polaritons

Hernández

Herrera

2019

The Journal of Chemical Physics

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We propose a cavity QED approach to describe light-matter interaction between an individual anharmonic molecular vibration and an infrared cavity field. Starting from a generic Morse oscillator with quantized nuclear motion, we derive a multi-level quantum Rabi model to study vibrational polaritons beyond the rotating-wave approximation. We analyze the spectrum of vibrational polaritons in detail and compare with available experiments. For high excitation energies, the spectrum exhibits a dense manifold of true and avoided level crossings as the light-matter coupling strength and cavity frequency are tuned. These crossings are governed by a pseudo parity selection rule imposed by the cavity field. We also analyze polariton eigenstates in nuclear coordinate space. We show that the bond length of a vibrational polariton at a given energy is never greater than the bond length of a bare Morse oscillator with the same energy. This type of bond hardening of vibrational polaritons occurs at the expense of the creation of virtual infrared cavity photons, and may have implications in chemical reactivity.Cavity quantum electrodynamics (QED) has been intensely studied for the development of quantum technology over the last decade [1,2]. Precision experiments under carefully controlled conditions have been implemented to reach the regime where quantum optical effects become relevant for applications [3][4][5]. Chemical systems and molecular materials at ambient conditions for long have been considered to be unnecessarily complex and uncontrollable to enable useful quantum optical effects. In recent years, the demonstration of reversible modifications of chemical properties in molecular materials via strong coupling to confined light has stimulated the study of cavity QED as an emerging research direction in chemical physics [6]. Light-matter interaction in the strong coupling (SC) and ultrastrong coupling (USC) regimes opens the possibility of creating novel hybrid photon-molecule states whose unique properties may enable novel applications in chemistry and material science.In the infrared regime, the coupling of an intramolecular vibration to the quantized electromagnetic vacuum of a Fabry-Pérot cavity can lead to the formation of vibrational polaritons [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. These hybrid light-matter states exhibit fundamentally novel properties in comparison with free-space vibrations. For instance, vibrational polaritons may enable the selective control of chemical reactions [21-23], a long-standing goal in physical chemistry [24]. Strong light-matter coupling provides a reversible way of modifying reactive processes without changing the chemical composition of materials, and also modify the radiative and non-radiative dynamics of molecular vibrations [25][26][27][28][29][30][31]. Several recent studies on vibrational strong coupling (VSC) within the ground electronic state have shown that chemical reactions can proceed through novel pathways in comparison with free space. Under VSC, r...

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“…[ [160][161][162][163] ESC Absorption and photoluminescence of vibronic polaritons in molecular ensembles. [74,118,131,164,165] VSC Linear and nonlinear spectroscopy of vibrational polaritons in molecular ensembles.…”

Section: A Recent Experimental Progressmentioning

confidence: 99%

Molecular polaritons for controlling chemistry with quantum optics

Herrera

Owrutsky

2020

The Journal of Chemical Physics

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This is a tutorial-style introduction to the field of molecular polaritons. We describe the basic physical principles and consequences of strong light-matter coupling common to molecular ensembles embedded in UV-visible or infrared cavities. Using a microscopic quantum electrodynamics formulation, we discuss the competition between the collective cooperative dipolar response of a molecular ensemble and local dynamical processes that molecules typically undergo, including chemical reactions. We highlight some of the observable consequences of this competition between local and collective effects in linear transmission spectroscopy, including the formal equivalence between quantum mechanical theory and the classical transfer matrix method, under specific conditions of molecular density and indistinguishability. We also overview recent experimental and theoretical developments on strong and ultrastrong coupling with electronic and vibrational transitions, with a special focus on cavity-modified chemistry and infrared spectroscopy under vibrational strong coupling. We finally suggest several opportunities for further studies that may lead to novel applications in chemical and electromagnetic sensing, energy conversion, optoelectronics, quantum control and quantum technology.

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Absorption and photoluminescence in organic cavity QED

Cited by 121 publications

References 80 publications

Collective Rayleigh Scattering from Molecular Ensembles under Strong Coupling

Collective Rayleigh Scattering from Molecular Ensembles under Strong Coupling

Multi-level quantum Rabi model for anharmonic vibrational polaritons

Molecular polaritons for controlling chemistry with quantum optics

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