Coherent Control with Modified Vacuum Fields

12 Aug 2024, 07:50 → 14 Aug 2024, 18:20 Europe/Stockholm

Albano Building 3

Gerrit Groenhof (University of Jyväskylä), Markus Kowalewski (Stockholm University)

Please be aware that scammers sometimes approach participants claiming to be able to provide accommodation and asking for credit card details. Do not give this information to them! If you are in any doubt about the legitimacy of an approach, please get in contact with the organizers.

Venue

Nordita, Stockholm, Sweden

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Scope

Coherent control of molecular dynamics by dressing potential energy surfaces with light has an enormous potential for photochemical applications in light harvesting, energy storage, opto-electronic and communication. In recent years this concept has been extended to modified vacuum fields as they are created by photonic structures that can confine specific light modes, such as optical cavities or nano-plasmonic structures. The increased interaction between those confined light modes and the molecules can lead to the formation of new hybrid light-matter states called polaritons. These polaritons are coherent superpositions of excitations of the molecules and of the light modes. The hybridization between light and matter not only delocalizes the excitation over many molecules but also changes their potential energy surfaces, and thus could be a new way to control chemistry, change optical material properties, and control energy transfer. Manipulating molecules with cavities requires a complete understanding of how the interaction with confined light affects the molecular dynamics. Thus, to unlock the full potential of manipulating chemistry with photonic structures, we urgently need a unified theoretical description of the strongly coupled light matter interaction that is sufficiently accurate to systematically design optical nano-structures for selectively altering reactivity. The new theoretical description needs to go significantly beyond the state of the art, as it needs to take into account the quantum nature of light. Therefore, the integration of the new theoretical framework into existing electronic structure and molecular dynamics methodologies will be a tremendous challenge and requires an interdisciplinary approach. With the workshop, we intend to overcome this challenge by bringing together researchers who are at the forefront of this field, either in theory or experiment. Ultimately, we expect to not only further our insights into strong light-matter coupling and its applications, but also to establish the new state of the art in understanding and predicting the effects of a modified vacuum on chemical reactivity.

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Themes and preliminary program schedule

We are planning a full 3 day program from Aug 12 to Aug 14. We thus recommend to plan arrival on Aug 11 and departure on Aug 15.

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Invited speakers

Claudia Climent

Kristín Björg Arnardóttir

Anael Ben-Asher

Marissa Weichmann

Agnes Vibok

Elisabetta Collini

Antonietta de Sio

Johannes Schachenmayer

Thomas Schnappinger

Tönu Pullerits

Jussi Toppari

Henrik Koch

Karl Borjesson

Christian Schaefer

Timur Shegai

Zhedong Zhang

Konstantinos Daskalakis

Dominik Sidler

Tomasz Antosiewicz 

Milan Delor 

Joel Yuen-Zhou

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Accommodation

Nordita has reserved a block rooms at the following hotels:

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Elite Hotel Arcadia | 20 Superior double room for single use - For details and reserving a room, click here. Last day to book your room is 14th of July.

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Biz Apartment Gärdet | 10 Studio small (single-use) and 10 Studio Medium (double-use) rooms - For reserving a room, contact at reservations@bizapartment.se. You can inform the hotel that you are making a reservation for the workshop by referring the code CCMVF. Last day to book your room is 11th of June.

1 - 3 nights: 
Small 1295 SEK/night incl. breakfast 
Medium 1395 SEK/night incl. breakfast

4+ nights: 
Small 1095 SEK/night 
Medium 1195 SEK/night

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All reservations, date adjustments and/or cancellations are to be made by the interested participant directly with the hotels.

Please be aware that scammers sometimes approach participants claiming to be able to provide accommodation and asking for credit card details. Do not give this information to them! If you are in any doubt about the legitimacy of an approach, please get in contact with the organizers.

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Application/Registration

Registration to be considered for on-site participation will close May 31st. Registrants will receive an on-site/remote participation confirmation from the organizers after this date.

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Sponsored by:

Monday, 12 August

Monday Morning: Mon - Morning Session

1 Opening

2 Robust modification of nuclear dynamics in cavity-coupled molecules in the large-N limit?

Theoretically explaining experimental observations of cavity-modified physics and chemistry remains to be a major challenge, in particular for a large number of coupled molecules. Here I discuss our bottom-up approach with minimal quantum optics many-body models, which include electronic, photonic, and motional degrees of freedom in their simplest form.

This talk will review how dark states acquire a "semilocalized" nature with unusual properties in terms of level statistics and other localization quantifiers. I then discuss how such states can play a crucial role for cavity-modified nuclear dynamics. As a main conclusion, I show that semilocalized states can produce exotic quantum states of motional wave-packets. Surprisingly, those features can remain robust, also in a large-N limit. I then present recent on-going work on how to extend these findings to more realistic models, using new types of advanced numerical approaches.

Speaker: Johannes Schachenmayer (CNRS & University of Strasbourg)

3 Cavity-induced non-adiabatic properties in molecular systems:Lindblad versus Schrödinger description

The exchange of energy between electronic and nuclear motion is the origin of non-adiabaticity and plays an important role in many molecular phenomena and pro-cesses. Conical intersections (CIs) of different electronic potential energy surfaces lead to the most singular non-adiabaticity and have been intensely investigated. The
coupling of light and matter induces conical intersections which are termed light-induced conical intersections (LICIs). There are two kinds of LICIs, those induced by classical (laser) light and those by quantum light like that provided by a cavity.
During the talk we present the subject of LICIs, discussing the achievements made so far. In contrast to natural CIs, the properties of which are dictated by nature, the properties
of their light-induced counterparts are controllable by choosing the frequency and intensity (or coupling to the cavity) of the external light source. This opens the door to inducing and manipulating various kinds of non-adiabatic effects. Several exam-ples of diatomic and polyatomic molecules are presented covering both dynamics and
spectroscopy. The computational methods employed are discussed as well. To our opinion, the young field of LICIs and their impact show much future potential.

Speaker: Ágnes Vibók (University of Debrecen)

10:15 Coffee Break

4 Is polaritonic chemistry a manifestation of a spin glass?

We demonstrate that the collective vibrational strong coupling of molecules in thermal equilibrium can give rise to significant local electronic polarizations in the thermodynamic limit. The discovered cavity-induced polarization pattern possesses a zero net polarization, which resembles a continuous form of a spin glass (or better polarization glass). Eventually, theoretical connections to well-known models of spin glasses are made explicit, along with their implications on polaritonic chemistry. For example, the existence of a spin glass phase could trigger an excess of thermal fluctuations that violate the fluctuation dissipation theorem and thus alter the thermodynamic properties of polaritonic systems.

Speaker: Dominik Sidler (Paul Scherrer Institut and Max Planck Institute for the Structure and Dynamics of Matter)

5 Cavity-Born-Oppenheimer Hartree-Fock: Vibronic-Strong-Coupling beyond a single molecule

When molecules are placed in a non-classical photonic environment present in optical or nanoplasmonic cavities, it is possible to form strong light-matter-coupled hybrid states called polaritons. Recent experiments show that this strong coupling between light and matter is capable of modifying chemical and physical properties and offer a possible novel approach to control chemical reactions. The situation in which the quantized cavity modes are coupled via their characteristic frequency to vibrational degrees of freedom of molecules is called vibrational strong coupling (VSC). In the VSC regime, the chemistry of a single electronic state (mostly the ground state) and its vibrational spectroscopy are influenced by the cavity interaction.

In this theoretical contribution, we use the ab-initio Cavity-Born-Oppenheimer-Hartree-Fock approach to study the effect of VSC on the ground state properties of single molecules and small ensembles of such molecules [1]. Our ab-initio treatment allows us to study the interactions between single molecules mediated by the cavity. These interactions give rise to local strong coupling effects that are likely to allow the modification of chemical reactivity in the VSC context. In a next step, we implemented analytical gradients and numerical Hessians within the Cavity-Born-Oppenheimer-Hartree-Fock framework [2]. The possibility to optimize cavity-coupled molecular systems revealed the importance of geometry relaxation and reorientation. Moreover, by introducing a vibro-polaritonic normal mode analysis, we are not only able to determine vibro-polaritonic IR spectra, but also to perform a comprehensive analysis of these hybrid states.

[1] T. Schnappinger et al., J. Phys. Chem. Lett., 14, 8024 (2023).
[2] T. Schnappinger et al., J. Chem. Theory Comput., 19, 9278 (2023).

Speaker: Thomas Schnappinger (Stockholm University)

12:15 Lunch break

Monday Afternoon: Afternoon Session

6 Ultrafast coherent exciton dynamics mediated by field-matter couplings

Strong coupling between electromagnetic radiation and matter is highly promising for tailoring optoelectronic and transport properties of functional materials, with potential applications ranging from organic photovoltaics to nanophotonics and quantum technologies. Strong coupling manifests in peak splittings in the optical spectra and ultrafast Rabi oscillations in the dynamics. The underlying processes involve a complex interplay of electronic, vibrational, and photonic degrees of freedom and occur on ultrashort, few 100s-fs timescales, thus demanding techniques combining high time resolution and the ability to unravel couplings. Here, we present some of our recent results using broadband two-dimensional electronic spectroscopy to probe couplings and track their quantum dynamics. In molecular aggregates of quadrupolar dyes on a gold nanoslit array, where molecular excitons are collectively coupled to spatially structured plasmonic fields, we observe coherent oscillations arising from plasmon-induced coherent exciton population transfer over mesoscopic distances at room temperature. In halide perovskites crystals, we demonstrate exciton Rabi oscillations driven by coherent phonon fields which behave essentially as the coupling of excitons to a field mode in an optical cavity. We show that even internal fields induced by low frequency coherent lattice motions can transiently control the ultrafast optical response in these materials. Our results suggest strategies for controlling ultrafast coherent dynamics in functional materials. Timmer et al, Nature Commun. 14, 8035 (2023); Nguyen et al, Nature Commun. 14, 1047 (2023)

Speaker: Antonietta De Sio

7 Polariton transport and chemistry under static and dynamic disorder

Polaritons exhibit delocalized wavefunctions resulting in enhanced energy transport compared to bare polar excitations. We developed a general method based on ultrafast far-field microscopy to directly image the transport of phonon-polaritons and exciton-polaritons from mid-IR to visible frequencies in a variety of environments, including microcavities, self-hybridized material slabs, two-dimensional materials, and plasmonic films, with femtosecond resolution and few-nanometer sensitivity to spatial motion. We leverage this approach to image polaritons over a wide temperature range, allowing us to systematically test the effect of both static and dynamic disorder on polariton transport and localization dynamics. I will discuss a few ways in which these results are allowing us to guide the optimization of polaritonic systems towards enhanced energy harvesting, single-photon gates and chemical selectivity.

Speaker: Milan Delor (Columbia University)

15:30 Coffee Break

8 Microcavity mediated excitation dynamics of photosynthetic light harvesting complexes

Strong light-matter interaction leads to the formation of hybrid polariton states and alters the photophysical dynamics of organic materials and biological systems without modifying their chemical structure. Here, we experimentally investigated a well-known photosynthetic protein, light harvesting 2 complexes (LH2) from purple bacteria under both strong and weak coupling with the light mode of a Fabry-Perot optical microcavity. Using femtosecond pump-probe spectroscopy, we analysed the polariton dynamics of the strongly coupled system. We observed a significant prolongation of the excited state lifetime compared with the bare exciton, which can be explained in terms of the exciton reservoir model. We also demonstrated cavity-mediated excitation transfer between different complexes even in case of weak effective light-mater interaction.

Speaker: Tönu Pullerits (Chemical Physics, Lund University)

9 Coherences of Molecular Polaritons Monitored by Multidimensional Spectroscopy

Strong light-molecule coupling has led to a new class of matter at nanoscale, due to its tunable hybridization of molecular excitations and photons known as polaritons. Because of the confined geometry that yields the collective nature, molecular polaritons create a new paradigm of molecular relaxation and radiative processes, i.e., reaction activity and light-induced exotic phases. These brought up great challenges for optical spectroscopy. The multidimensional spectroscopy, by introducing several delays and gates between laser pulses, is powerful for studying the molecular relaxation and photochemistry. This delivers a versatile tool for a real-time monitoring of nonequilibrium molecular dynamics, but not clear yet for polaritons. The collective interactions result in the long-range quantum coherence, which creates new relaxation channels and spectroscopic probes of molecular polaritons.

In this talk, I will present an overview of our recent works on the multidimensional spectroscopy for molecular polaritons. We developed a microscopic theory for the 2D spectroscopy of molecules in microcavities, using the density matrix and Langevin equation. A new capability of resolving multiple channels and timescales of polariton dynamics with high time-frequency scale is demonstrated. The results manifest coherent couplings in a trade-off with the dark states. The dark states show a high mode density and localized nature, which have significant contribution to the population and coherence of polaritons. Our work provides a power theory and approach for a unified understanding of the spectroscopic signals measured in recent experiments on molecular polaritons.

Speaker: Zhedong Zhang (City University of Hong Kong)

10 Recent advances in ab initio modeling of molecular polaritons

Polaritonic and plasmonic chemistry is an interdisciplinary emerging field that presents several challenges and opportunities in chemistry, physics, and engineering. Cavities offer non-invasive ways to modulate and control molecular properties – and study unique states of matter (polaritons). In this talk, I will discuss our recent advances in the theoretical and computational modeling of molecules interacting strongly with quantum fields in optical cavities and metallic nanostructures. I will focus on the new time-dependent implementation that can be used to simulate energy transfer between molecules and up- and down-conversion of photons. If time permits, I will also show our simulations of chiral cavities that open the possibility of controlling enantioselectivity and introducing asymmetry in chemical reactions.

Speaker: Prof. Henrik Koch (Norwegian University of Science and Technology, Trondheim, Norway)

Poster session

11 Ultra-strong light matter coupling with itinerant electrons

The interaction between matter and the quantum fluctuations of light in cavities can lead to novel exotic states of matter. Previous theoretical investigations into this area have produced conflicting outcomes, creating obstacles for further research. In this talk, I pinpoint the source of these discrepancies to the inherently divergent nature of local quantum light fluctuations in vacuum. To overcome this challenge, we introduce a new computational approach that calculates the effective mass changes in free electrons due to alterations in the local photon density of states within cavities compared to free space. Our findings demonstrate a slight reduction in electron mass in Fabry-Perot cavities, contrary to earlier studies. Meanwhile, surface phonon polaritons are shown to significantly increase electron mass, potentially achieving ultra-strong coupling. This highlights surface phonon polaritons as a promising avenue for controlling the properties of 2D materials.

Speaker: Marios Michael (Max Planck Institute for the Structure and Dynamics of matter)

12 A Discrete Truncated Wigner Approximation approach to polariton dynamics

Experiments in polaritonic chemistry have demonstrated that the collective coupling of molecules to a cavity can modify chemical reactions. These modifications could come from genuine quantum effects and the study of the full quantum dynamics is thus of high interest for such systems. Efficiently computing quantum many-body dynamics has been a very challenging goal and many attempts with different methods were proposed. Here, we try an approach based on the so-called Truncated Wigner Approximation (TWA) and its version for discrete systems, the Discrete Truncated Wigner Approximation (DTWA). Comparisons with exact solutions of some simple systems with mixed discrete and continuous degrees of freedom show the power and the limits of the methods. We demonstrate a good capability of the methods to capture exact dynamics for quadratic potentials in continuous systems and for two-body interactions in discrete systems. These previous results motivate us to apply TWA/DTWA techniques to a disordered Holstein-Tavis-Cummings model, a toy model for polaritonic chemistry.

Speakers: Johannes Schachenmayer (CNRS & University of Strasbourg), Maxence Pandini (CESQ/ISIS, CNRS & University of Strasbourg)

13 Atomistic resolution simulations of molecules in nanocavities

Discrepancy between atomistic molecular dynamics and experiment can arise, among other things, from the difference in the number of molecules that are considered, making the direct comparison between simulation and experiment often ambiguous. Especially for investigating phenomena that directly depend on the number of molecules, such as strong coupling between light and matter, a meaningful direct comparison would be highly desirable to gain understanding from both methods. Plasmonic nanocavities have been experimentally reported to provide an environment supporting few or even single-molecule strong coupling [1,2], making them ideal templates to build atomistic simulation models [3] with as many (or as few) molecules as in experiment and thus enable more direct comparison. The atomistic resolution of the simulations provides valuable insights into conditions governing strong coupling in terms of the system’s geometry, conformation and dynamics, improving understanding and promoting design of new systems. As a proof of concept of such simulation platform, we present an atomistic model of the full plasmonic nanocavity system in reference [1] consisting of the gold nanoparticle on top of the gold surface (nanoparticle-on-mirror geometry) with the emitter molecule(s) (methylene blue) encapsulated by scaffold molecules (cucurbit-[7]-uril) in the gap region.

[1] Chikkaraddy R, de Nijs B, Benz F, et al. Single-molecule strong coupling at room temperature in plasmonic nanocavities. Nature. 2016;535(7610):127-130. doi:10.1038/nature17974.

[2] Heintz J, Markešević N, Gayet E, et al. Few-Molecule Strong Coupling with Dimers of Plasmonic Nanoparticles Assembled on DNA. ACS Nano. 2021;15(9):14732-14743. doi: 10.1021/acsnano.1c04552.

[3] Luk HL, Feist J, Toppari JJ, Groenhof G. Multiscale Molecular Dynamics Simulations of Polaritonic Chemistry. J Chem Theory Comput. 2017; 12;13(9):4324-4335. doi: 10.1021/acs.jctc.7b00388.

Speaker: Emmi Pohjolainen (University of Jyväskylä)

14 Coupling Polyatomic Molecules to Lossy Nanocavities: Lindblad versus Schrödinger description

The use of cavities to impact molecular structure and dynamics has become popular. As cavities, in particular plasmonic nanocavities, are lossy and the lifetime of their modes can be very short, their lossy nature must be incorporated into the calculations. The Lindblad master equation isommonly considered as an appropriate tool to describe this lossy nature. This approach requires the dynamics of the density operator and is thus substantially more costly than approaches employing the Schrödinger equation for the quantum wave function when several or many nuclear degrees of freedom are involved. In this work we compare numerically the Lindblad and Schrödinger descriptions discussed in the literature for a molecular example where the cavity is pumped by a laser. The laser and cavity properties are varied over a range of parameters. It is found that the Schrödinger description adequately describes the dynamics of the polaritons and emission signal as long as the laser intensity is moderate and the pump time is not much longer than the lifetime of the cavity mode. Otherwise, it is demonstrated that the Schrödinger description gradually fails. We also show that the failure of the Schrödinger description can often be remedied by renormalizing the wave function at every step of the time propagation. The results are discussed and analyzed.

Speaker: Gábor Halász (University of Debrecen)

15 Extending the Tavis-Cummings model for molecular ensembles - Exploring the effects of dipole self energies and static dipole moments

Strong coupling of organic molecules to the vacuum field of a nanoscale cavity can be used to modify their chemical and physical properties. We extend the Tavis-Cummings model for molecular ensembles and show that the often neglected interaction terms arising from the static dipole moment and the dipole self-energy are essential for a correct description of the light-matter interaction in polaritonic chemistry. On the basis of a full quantum description, we simulate the excited-state dynamics and spectroscopy of MgH+ molecules resonantly coupled to an optical cavity. We show that the inclusion of static dipole moments and the dipole self-energy is necessary to obtain a consistent model. We construct an efficient two-level system approach that reproduces the main features of the real molecular system and may be used to simulate larger molecular ensembles.

Speaker: Lucas Garcia Borges (Stockholm University)

16 Gauge Invariant Truncated Models in Cavity Quantum Electrodynamics

Resolving gauge ambiguities for truncated matter models coupled to quantum light has received a lot of attention recently. Equivalence of the dipole gauge and the coulomb gauge Hamiltonians was achieved by properly constructing unitary operators in the truncated matter subspace. We revisit these ideas and discuss gauge invariance in a general setting, not necessarily restricted to the dipole or the coulomb gauges. Our framework is based on gauge-invariant projectors such that there is a separate basis set for each gauge. As the result, approximation error is invariant. In the end, we discuss how to build optimally truncated gauge-invariant lattice models using Machine Learning techniques.

Speaker: Anatoly Obzhirov (MPI Hamburg)

17 Insights into the mechanisms of optical cavity-modified ground-state chemical reactions

In this presentation, we employ a numerically exact, fully quantum dynamical approach to systematically investigate the mechanisms underlying the rate modification of ground-state chemical reactions inside an infrared optical cavity under the vibrational strong coupling regime.

First of all, we've revealed that static quantum features such as zero-point energy and pure tunneling effects are not the major cause of the observed resonant rate peak.

Secondly, we proposed a mechanistic insight into this resonant rate modification. The resonant chemical reactivity alternation can be rationalized by the opening of cavity-induced intramolecular and intermolecular reaction pathways. A cavity-induced intramolecular reaction pathway involves two distinct energy exchange processes. The first energy exchange is between molecular vibrations and the cavity radiation mode, which enforces the resonant condition, where the photon energy matches a dipole-allowed molecular vibrational transition. The second energy exchange occurs between the cavity radiation mode and its surrounding bath, facilitating the thermalization of the cavity mode and thus ensuring the sustainability of the former energy exchange process in the long run. Furthermore, the collective coupling of molecules to a resonant cavity mode can also initiate an intermolecular reaction pathway, which is a fourth-order effect with respect to the light-matter coupling strength. These cavity-promoted intra- and intermolecular reaction pathways remain unaffected, regardless of whether the molecular dipole moments are aligned in the same or opposite direction as the light polarization, which means that the rate alternation can survive in an anisotropic ensemble.

Thirdly, a strong anharmonic reaction can exhibit multiple peaks, and their heights are determined jointly by several kinetic factors.

Lastly, we conduct a comparative analysis by juxtaposing the mixed quantum-classical results with fully quantum mechanical simulations. In this mixed quantum-classical approach, the cavity radiation mode is treated classically with a mean-field nuclear force averaging over the remaining degrees of freedom, both within the system and the environment, which are handled quantum. Through this comparison, we confirm that a quantum-mechanical description of both cavity mode and molecular vibrations is imperative in reproducing the resonant peak observed in the cavity frequency-dependent rate profile.

Speaker: Yaling Ke (ETH Zürich)

18 Interaction between polyatomic molecules on layered surfaces beyond the dipole approximation

For aggregates of molecular monomers above layered surfaces, the dipole approximation breaks down when the distance between monomers and surfaces is less than several nanometers. To overcome this problem, we employ macroscopic quantum electrodynamics and use the complete transition current density of the individual monomers. Within this framework, the resulting Master Equation for the excitonic degrees of freedom of the aggregate is derived.

Speaker: Hsiao-Han Chuang (Max Planck Institute for the Physics of Complex Systems)

19 Nucleophilicity of Water and Alcohols: Measuring Kinetics under Vibrational Strong Coupling.

Vibrational Strong Coupling (VSC) has recently been shown to alter the rates and selectivity of polar chemical reactions –reactions in which electrophiles and nucleophiles combine. However, measuring reliable reaction kinetics under VSC remains an important challenge which hinders our ability to know which specific elementary properties of polar reactions are affected by VSC. We herein set out to test whether VSC influences the nucleophilicity of alcohols and water, which are commonly involved species in previous studies on VSC. We determined the rate constants for the nucleophilic capture of the nucleophiles with a library of benzhydrylium ions as reference electrophiles with and without strong coupling of the nucleophile’s key vibrations. Using recently developed fixed-width cavities enabled the obtention a large kinetic dataset with remarkably small errors. For all investigated combinations of electrophiles and nucleophiles, only small changes in the rate constants of the reactions were observed independently of the coupled bands. These results suggest that VSC does not substantially alter the nucleophilicity of water and alcohols, suggesting that polar reactions are modified through other, presently unknown, mechanisms.

Speaker: Cyprien Muller (University of Strasbourg)

20 Towards new photochemistry with quantum electrodynamics coupled cluster theory

When light and matter strongly interact, polaritonic states with mixed electronic and photonic character emerge. As a consequence, new photochemical pathways become available under strong coupling conditions. In order to get insight on the mechanism underlying these modifications, theoretical studies using accurate ab initio methods are fundamental. In particular, Quantum Electrodynamics - Coupled Cluster theory (QED-CC) has been recently proposed as a suitable method to describe electron and electron-photon correlation. However, coupled cluster theory is known to provide unphysical complex energies at degeneracy points between states with the same symmetry.
In this poster, we explore how a quantized electromagnetic field can alter conical intersections and thereby modify photochemical processes. We highlight how the well-known numerical artifacts in coupled cluster theory can still be found in its generalization to quantum electrodynamics, and we propose a new parametrization that is able to correctly describe conical intersections between states with the same symmetry. This method, together with an efficient implementation of excited state gradients and non-adiabatic couplings, will allow to accurately study excited state dynamics in strong coupling conditions.

Speaker: Sara Angelico (Norwegian University of Science and Technology (NTNU))

21 Training machine learning potentials for studying dynamics under vibrational strong coupling

Machine learning potentials have recently been used to simulate chemical dynamics under vibrational strong coupling, in order to gain greater insight into the underlying microscopic mechanisms [1]. These machine learning potentials are trained on data from density functional theory and are used to evaluate the forces during molecular dynamics simulations, which facilitates atomistic insight into the effect of a cavity on the chemical dynamics. Here, the training of such machine learning potentials is explained. The approach is illustrated by applying the method to study the dynamics of water under vibrational strong coupling. [1] C. Schäfer, J. Fojt, E. Lindgren, and P. Erhart, J. Am. Chem. Soc. 2024, 146, 8, 5402–5413

Speaker: Esmée Berger (Chalmers University of Technology)

22 Ultrafast and Coherent Dynamics in Strong Coupled Light-Matter Systems through Two-Dimensional Electronic Spectroscopy (2DES)

The ability to manipulate light at the nanoscale is greatly enhanced by the tremendous progress done in the field of plasmonic nanoparticles. Their high versatility enables the confinement and control of very strong electric fields, making these nanosystems ideal candidates for polaritonic states formation when combined with strong quantum emitters, such as molecular excitons. The resulting polaritonic nanosystems, known as plexcitonic nanosystems, offer immense potential due to their tunable optical properties at the nanoscale. In the realm of nanophotonics and quantum technologies, advanced techniques such as two-dimensional electronic spectroscopy (2DES) and pump-probe methods provide a means to explore the ultrafast and coherent dynamics of these systems. Despite the progress made, the intricate ultrafast dynamics involved in hybrid light-matter states remain incompletely understood, prompting our focus in this research. In our works we couple colloidal gold nanorods with organic dyes to achieve the strong coupling condition. Subsequently, we conduct a comprehensive analysis of the coherent and incoherent ultrafast behaviors of uncoupled colloidal gold nanorods, followed by a comparative study with plexcitonic nanosystems. The objective of our research is to contribute to an exhaustive understanding and exploitation of strong light-matter interactions at the nanoscale. We believe that our findings will advance the fundamental understanding of these phenomena but also pave the way for practical applications in the development of nanophotonic and quantum technologies.

Speaker: Federico Toffoletti (University of Padova)

23 Understanding the cavity Born–Oppenheimer approximation

Experiments have demonstrated that vibrational strong coupling between molecular vibrations and light modes can significantly change molecular properties, such as ground-state reactivity. Theoretical studies toward the origin of this exciting observation can roughly be divided into two categories. On the one hand, there are studies based on Hamiltonians that simply couple a molecule to a cavity mode via its ground-state dipole moment; on the other hand we have ab initio calculations that self-consistently include the effect of the cavity mode on the electronic ground state within the cavity Born-Oppenheimer (CBO) approximation. These two approaches are not equivalent; the CBO approach is more rigorous, but unfortunately it requires the rewriting of electronic-structure code, and its results may sometimes be hard to physically interpret.

In this poster, I will explain how to exploit the relation between the two approaches and demonstrate on a real molecule (hydrogen fluoride) that for realistic coupling strengths, we can recover CBO energies and spectra to high accuracy using only out-of-cavity quantities from standard electronic-structure calculations. In doing so, it becomes clear what physical effects underly the CBO results. This methodology can aid in incorporating more possibly important features in models, play a pivotal role in demystifying CBO results, and provide a practical and efficient alternative to full CBO calculations.

Speaker: Marit Fiechter (ETH Zürich)

Tuesday, 13 August

Tuesday Morning: Morning 1

24 New Experimental Platforms for Polariton Reaction Dynamics

Polaritons are hybrid light-matter states with unusual properties that arise from strong interactions between a molecular ensemble and the confined electromagnetic field of an optical cavity. Cavity-coupled molecules can demonstrate energetics, reactivity, and photophysics dramatically distinct from their free-space counterparts, but the mechanisms and scope of these phenomena remain open questions. I will discuss new experimental platforms that the Weichman Lab is developing to investigate molecular reaction dynamics under vibrational strong coupling.

While polaritons are now well-established in solution-phase and solid-state systems, they had not been previously reported in isolated gas-phase molecules, where attaining sufficiently strong light-matter interactions is a challenge. We access the strong coupling regime in an intracavity cryogenic buffer gas cell optimized for the preparation of simultaneously cold and dense ensembles and report a proof-of-principle demonstration in gas-phase methane. We strongly cavity-couple individual rovibrational transitions and probe a range of coupling strengths and detunings. In upcoming work, we will harness this infrastructure as a new testbed for fundamental studies of polariton physics and chemistry.

We are also searching for signatures of cavity-altered dynamics in benchmark solution-phase systems. So far, we have focused on radical hydrogen-abstraction processes, which have well-characterized reactive surfaces and can be initiated with photolysis and tracked directly on ultrafast timescales. We use ultrafast transient absorption to examine intracavity reaction rates with the goal of better understanding exactly how and when reactive trajectories may be influenced by strong light-matter interactions.

Speaker: Marissa Weichman (Princeton University)

25 Simulating chemical dynamics under vibrational strong coupling, what to take from it, and where to go next

Polaritonics has demonstrated remarkable capabilities, including the non-intrusive control over chemical reactivity and solvation dynamics.
Our understanding of the underlying microscopic mechanism is limited, at best, largely caused by a lack of predictive theory that is able to connect to experimental observables. Here, I will present our recent attempts in overcoming this challenge using ab initio QED [1] and machine learning [2,3].
We will briefly discuss the question to which extend electronic polarization might play an underappreciated role and how this could be connected to changes in solvation [4]. The talk will close with an outlook towards new direction in chiral polaritonics [5,6] and plasmonic catalysis [7].

[1] C. Schäfer, J. Flick, E. Ronca, P. Narang, and A. Rubio, Nature Communications, (2022) 13:7817.
[2] C. Schäfer, J. Fojt, E. Lindgren, and P. Erhart, J. Am. Chem. Soc. 2024, 146, 8, 5402–5413.
[3] C. Schäfer, Phys. Chem. Lett. 2022, 13, 30, 6905-6911.
[4] M. Castagnola, T. Haugland, E. Ronca, H. Koch, C. Schäfer, J. Phys. Chem. Lett. 2024, 15, 5, 1428–1434.
[5] C. Schäfer, D. Baranov, J. Phys. Chem. Lett. 2023, 14, 15, 3777-3784.
[6] D. Baranov, C. Schäfer, M. Gorkunov, ACS Photonics 2023, 10, 8, 2440-2455.
[7] J. Fojt, P. Erhart, C. Schäfer, to be submitted.

Speaker: Christian Schäfer (Chalmers)

26 Simulating (ro)vibrational polaritons: (1) an efficient and flexible approach, (2) the consequences of the Pauli principle

In this poster I present two topics:

(1) A theoretical framework is presented for the computation of rovibrational polaritonic states of a molecule in a lossless infrared (IR) microcavity.
In the proposed approach the quantum treatment of the rotational and vibrational motion of the molecule can be formulated using arbitrary approximations. The cavity-induced changes in electronic structure are treated perturbatively, which allows using the existing polished tools of standard quantum chemistry for determining electronic molecular properties.
As a case study, the rovibrational polaritons and related thermodynamic properties of H$_2$O in an IR microcavity are computed for varying cavity parameters and applying various approximations to describe the molecular degrees of freedom.

(2) The consequences of enforcing permutational symmetry, as required by the Pauli principle (spin-statistical theorem), on the state space of molecular ensembles interacting with the quantized radiation mode of a cavity are discussed.
The Pauli-allowed collective states are obtained by means of group theory, i.e., by projecting the state space onto the appropriate irreducible representations of the permutation group of the indistinguishable molecules.
It is shown that with increasing number of molecules the ratio of Pauli-allowed collective states decreases very rapidly, bosonic states are more abundant than fermionic states, and the brightness of the Pauli-allowed state space increases(decreases) with increasing fine structure in the energy levels of the material ground(excited) state manifold.
Numerical results are shown for the realistic example of rovibrating H$_2$O molecules interacting with an infrared cavity mode.

Speaker: Tamás Szidarovszky (Eötvös Loránd University)

10:20 Coffee break

27 Targeting the dark states in strongly coupled systems

Strong light-matter coupling generates hybrid states that inherit properties of both light and matter, effectively allowing the modification of the molecular potential energy landscape. This phenomenon opens a plethora of options for manipulating the properties of molecules, with a broad range of applications in physics, chemistry, and materials science. In this presentation, I will focus on the topic of dark states. I will discuss a method to vary the number of dark states in Fabry Perot cavities. This by varying the cavity mode. The presented approach could become a valuable tool for assessing the effect of dark states on photochemistry. I will further outline my plans to use kinetic modelling to extract the number of dark states from spectroscopical data. Towards the end of my talk, I will highlight the idealness of polaritons. That for the common case, there is not two bright states and a set of dark states. Instead, states have various shades of grey. There is thus a need to both theoretically account for this greyness, and experimentally device methods to create systems that are more ideal. I will show our results of trying to make highly ideal polaritons in the ultra-strong coupling regime.

Speaker: Karl Börjesson (the University of Gothenburg)

28 Ultra-fast photochemistry under strong light-matter coupling

Strong coupling between photoactive molecules and confined light modes results in the formation of hybrid light-matter states, polaritons, with energies above and below the original states of the molecule and cavity. This has been shown to alter the photochemistry of the molecules [1], but the details of this effect remains largely unknown. In a typical Fabry-Pérot cavity strong coupling is achieved by introducing the coupled molecule inside the cavity in sufficient concentration. However, with the increasing concentration the number of dark states, i.e., molecular states without photonic contribution, increases in proportion. Simulations and experiments suggest that the polaritonic states, including the dark states, follow Kasha’s rule and relax to the lowest energy state available for the system before decaying [2–5]. This opens possibilities to utilize the delocalized character of polariton states for energy transfer and/or light-harvesting [4]. We have studied the effect of the Stokes shift of the molecule to its relaxation pathway and involved processes [2,5].

Recently, we have investigated the influence of strong light-matter coupling on an ultra-fast photochemical reaction, i.e., the excited-state intramolecular proton transfer (ESIPT), of 10-hydroxybenzo[h]quinoline (HBQ) [6]. The reaction happens within ~15 fs which is of the same order as lifetimes of our low-Q cavities. We observe that the excitation spectrum under strong coupling is a product of the excitation spectrum of the ”bare” molecules and the absorption spectrum of the molecule-cavity system. This suggest that the polaritons can act as gateways to efficiently channel excitations into molecules, which can then react ”normally”. Furthermore, this channeling process depends mainly on the spectral overlap between the polariton and the molecular dark states [2]. Since this overlap increases with increasing HBQ concentration, we see enhancement of ESIPT as a function of the coupling strength [6], in contrast to suppression as suggested by the theoretical models that predict a modified potential energy surface with a barrier to the reaction. Our results show that the the formation of the modified polaritonic potential energy surface is prevented by the energetic disorder at the ambient conditions. Our findings are important in the context of polaritonic chemistry, where influencing photochemical reactions via strong light-matter coupling is crucial.

1. R. Bhuyan, J. Mony, O. Kotov, G. W. Castellanos, J. Gómez Rivas, T.O. Shegai, K. Börjesson, Chem. Rev. 123, 10877–10919 (2023).
2. G. Groenhof, C. Climent, J. Feist, D. Morozov, J.J. Toppari, J. Phys. Chem. Lett., 10, 5476-5483 (2019); H.L. Luk, J. Feist, J.J. Toppari, G. Groenhof, J. Chem. Theory Comput. 13, 43244335 (2017).
3. S. Baieva, O. Hakamaa, G. Groenhof, T.T. Heikkila, J.J. Toppari, ACS Phot. 4, 2837 (2017).
4. G. Groenhof, J.J. Toppari, J. Phys. Chem. Lett. 9, 4848 (2018).
5. E. Hulkko, S. Pikker, V. Tiainen, R.H. Tichauer, G. Groenhof, J.J. Toppari, J. Chem. Phys. 154, 154303 (2021).
6. A. Dutta, V. Tiainen, L. Duarte, I. Sokolovskii, N. Markešević, D. Morozov, H.A. Qureshi, S. Pikker, G. Groenhof, J.J. Toppari, https://www.researchsquare.com/article/rs-3237899/v1

Speaker: Prof. Jussi Toppari (Nanoscience Center & Department of Physics, University of Jyväskylä)

29 Excitation energy transfer in disordered organic polaritons: Does it matter if they are dark or bright?

Placing organic molecules in an optical cavity holds a great promise for the improvement of excitation energy transfer in such molecules due to the hybrid nature of the emerging light-matter quasiparticles, called polaritons. Recently, it was envisaged that a large static disorder of molecular excitation energies could benefit the transport of polaritons even further, leading to the so-called disorder-enhanced transport (DET) regime [1-5]. Under realistic conditions, the thermal motion of molecules additionally results in dynamic disorder, the effect of which on the polariton transport remains unclear. Therefore, it raises an open question on whether the DET regime is possible under realistic conditions, when molecular motions and interactions with the environment lead to continuous redistribution of the excitation energies. To address this question, we used multiscale molecular dynamics simulations of molecules with various absorption linewidth. The results of our simulations provide detailed insights into the influence of static and dynamic disorder on the polariton transport.

References:
[1] J. Schachenmayer, C. Genes, E. Tignone, and G. Pupillo. PRL, 2015, 196403.
[2] N. C. Chávez, F. Mattiotti, J. A. Méndez-Bermúdez, F. Borgonovi, and G. L. Celardo, PRL, 2021, 153201.
[3] T. F. Allard and G. Weick. Phys. Rev. B, 2022, 245424.
[4] G. Engelhardt and J. Cao. PRL, 2023, 213602.
[5] G. J. R. Aroeira, K. T. Kairys, and R. F. Ribeiro, J. Phys. Chem. Lett., 2023, 5681–5691.

Speaker: Ilia Sokolovskii (University of Jyväskylä)

12:20 Lunch

13:15 Social activity

18:00 Conference Dinner

Wednesday, 14 August

Wednesday Morning: Morning 1

30 Coherent dynamics in solutions of colloidal plexcitonic nanohybrids at room temperature

The increasing ability to prepare systems with nanoscale resolution and address their optical properties with ultrashort time precision is revealing quantum phenomena with tremendous potentiality in quantum nanotechnologies. Colloidal plexcitonic materials promise to play a pivotal role in this scenario. Plexcitons are hybrid states originating from the mixing of the plasmon resonances of metal nanostructures with molecular excitons. They allow nanoscale confinement of electromagnetic fields and the establishment of strong couplings between light and matter, potentially giving rise to controllable and tunable coherent phenomena. However, the characterization of the ultrafast coherent and incoherent dynamics of colloidal plexciton nanohybrids remains highly unexplored. Here, 2D electronic spectroscopy is employed to study the quantum coherent interactions active after the photoexcitation of these systems. By comparing the response of the nanohybrids with the one of the uncoupled systems, the nonlinear photophysical processes at the base of the coherent dynamics were identified, allowing a step forward toward the effective understanding and exploitation of these nanomaterials.

Speaker: elisabetta collini (Dept of Chemical Sciences, University of Padova)

31 Strong light-matter coupling: from self-hybridized polaritons to Casimir self-assembly

Timur O. Shegai

Department of Physics, Chalmers University of Technology, Gothenburg, 412 96, Sweden

Email: timurs@chalmers.se

Abstract:

Strong light-matter interactions are at the core of many electromagnetic phenomena. In this talk, I will give an overview of several nanophotonic systems which support polaritons – hybrid states of light and matter, as well as try to demonstrate their potential usefulness in applications. I will start with transition metal dichalcogenides (TMDs) and specifically discuss one-dimensional edges in these two-dimensional materials [1-2]. I will also discuss the concept of self-hybridization, a scenario in which both light and matter subparts in a polaritonic system are supported by one and the same (nano)structured material [3]. I will demonstrate such self-hybridization in TMD nanostructures [1-2] and levitating water droplets [4]. The latter is interesting, due to abundance of such water droplets in natural systems, including mists, fogs, and clouds. Furthermore, I will show that Fabry-Pérot resonators, one of the most important workhorses of nanophotonics, can spontaneously form in an aqueous solution of gold nanoflakes [5-7]. This effect is possible due to the intricate balance between attractive Casimir-Lifshitz forces and repulsive electrostatic forces acting between the flakes. There is a hope that this technology is going to be useful for future developments in self-assembly and polaritonics, as well as help develop a unified view of Casimir and strong light-matter coupling phenomena.

ACKNOWLEDGEMENT
This work was supported by Swedish Research Council (grant no. 2022-03347), Knut and Allice Wallenberg foundation (grant no. 2019.0140), Vinnova 2D-Tech competence center (ref. 2019-00068), and Olle Engkvists foundation (grant no. 211-0063).

REFERENCES
[1] Nat. Commun., 11, 4604, (2020)
[2] Laser & Photonics Rev., 17, 2200057, (2023)
[3] J. Chem. Phys., 154, 024701, (2021)
[4] Phys. Rev. Lett., 132, 193804, (2024)
[5] Nature, 597, 214-219, (2021)
[6] Nat. Phys., 19, 271-278, (2023)
[7] Sci. Adv., 10, eadn1825, (2024)

Speaker: Prof. Timur Shegai (Chalmers University of Technology)

10:00 Coffee Break

32 Polariton lineshape in the presence of energetic disorder

The polaritonic optical response of molecules positioned in optical cavities is strongly influenced not only by the molecule-cavity modes coupling and the detuning between the photon and the emitter's transition frequency, but also by the spectral distribution of the molecular emitters (that outside the cavity determine the observed lineshape). While the effect of inhomogeneous broadening of the emitter has been investigated in the past, with interesting observations such that polaritons do not inherit the static disorder broadening, a general analytical theory describing such phenomenon is absent. In this talk I will discuss our recent work where we apply the Kubo-Anderson stochastic theory of molecular spectral lineshape to the case of polaritons formed in the collective strong coupling regime. I will discuss both the fast and slow limits of the random frequency modulation of the emitter as well as the intermediate regime and show how the interplay between the characteristic timescales of the cavity and the molecular disorder is expressed in the observed polaritons lineshapes.

Speaker: Clàudia Climent

33 Memory loss is contagious in open quantum systems

The coupling of a system to more than one kind of environment is ubiquitous in nature. For example, in the field of polaritonic chemistry, where the interaction with confined light modifies the molecular reactivity, typically both an optical bath and a phononic bath are involved. In such cases, it is crucial to account for the interplay between these two different environments, which cannot be treated separately [PRX Quantum 3(1), 010321 (2022)]. In this talk, I will discuss the interplay between the memory effects of the two baths. In particular, we will consider cases where one bath, e.g., an electromagnetic environment, is Markovian (memoryless) and can be treated by introducing lossy terms into the system, and the other, e.g., a vibrational bath, is structured. We show that although the interaction between a structured bath and a system is typically non-Markovian, it becomes Markovian when taking into account the system's interaction with the memoryless bath [arXiv:2402.16096 (2024)]. This demonstrates that the memoryless property can be transferred from one bath to another through the system with which they both interact.

Speaker: Anael Ben Asher

12:00 Lunch break

Wednesday Afternoon: Afternoon 1

34 The Secret Life of a Polaritonic Chemistry Experiment

The prospect of modifying chemical processes by strong coupling molecules to vacuum fields is one that has generated a huge level of excitement [1]. However, concerns around the reproducibility of key experiments and a greater appreciation of the complexity of cavity-based physics have led to increasing caution in how experimental results are interpreted [2, 3].

In this talk I will argue that an unsystematic approach to polaritonic chemistry experiments can make it difficult to disentangle a variety of competing effects:

1. Non-polaritonic phenomena can produce measurable effects that can be misattributed to strong coupling [4].
2. Strong coupling can produce unexpected polaritonic side-effects that can lead to errors in the estimation of chemical reaction rates [5].
3. Cognitive bias can cause us to misattribute an apparent change in material properties to strong coupling [6].

These results emphasise the importance of systematic experimentation and further highlight the need for a deeper understanding of the fundamentals of strong coupling and chemistry in multimode cavities.

References:

1. F. J. García-Vidal, C. Ciuti & T. W. Ebbesen. “Manipulating matter by strong coupling to vacuum fields.” Science 2021, 373, eabd0336
2. B. S. Simpkins, A. D. Dunkelberger & J. C. Owrutsky. “Mode-Specific Chemistry through Vibrational Strong Coupling (or A Wish Come True).” J. Phys. Chem. C 2021, 125, 19081.
3. T. Khazanov et al. “Embrace the darkness: An experimental perspective on organic exciton–polaritons.” Chem. Rev. Phys. 2023, 4, 041305.
4. P. A. Thomas et al. “Non-Polaritonic Effects in Cavity-Modified Photochemistry.” Adv. Mater. 2024, 36, 2309393.
5. P. A. Thomas & W. L. Barnes. “Strong coupling-induced frequency shifts of highly detuned photonic modes in multimode cavities.” Under Review.
6. P. A. Thomas & W. L. Barnes. “Selection Bias in Strong Coupling Experiments.” J. Phys. Chem. Lett. 2024, 15, 6, 1708–1710.

Speaker: Philip Thomas (University of Exeter)

35 Organic light-emitting diodes in the strong light-matter regime

In this presentation, I discuss our recent study investigating the influence of strong coupling in polariton organic light-emitting diodes using time-resolved electroluminescence studies [1]. We fabricated bottom-emitting polariton OLEDs, employing the well-established polariton TDAF molecular semiconductor between aluminium electrodes. Our analysis, based on a model of coupled rate equations, considered all major mechanisms contributing to delayed electroluminescence in organic emitters. We found that in our devices emission dynamics remained unmodified in the presence of strong coupling.

I will also discuss the prospects of strong coupling and photonics as an alternative route to investigate material properties that are usually inaccessible. This direction may offer new avenues for OLEDs to benefit from polaritonic research [2].

[1] Abdelmagid, Qureshi, Papachatzakis, Siltanen, Kumar, Ashokan, Salman, Luoma, Daskalakis, Nanophotonics, 8986, 1–9 (2024).

[2] Palo, Papachatzakis, Abdelmagid, Qureshi, Kumar, Salomaki, and Daskalakis, The Journal of Physical Chemistry C 127, 14255, (2023).

Speaker: Prof. Konstantinos Daskalakis (University of Turku)

36 Molecular polaritons as quantum impurity models

In the collective strong coupling regime where N molecules couple to an optical cavity mode, molecular polaritons may be regarded as quantum impurity models, where the impurity is a photon and the complex anharmonic molecular degrees of freedom serve as a bath. If this bath is large enough (N>>1), as in the case of most molecular polariton experiments, the quantum dynamics of such a system becomes very simple to compute [1,2], as demonstrated in our recent method, Collective Dynamics using Truncated Equations (CUT-E) [3,4]. The conceptual implications of this method are also discussed in light of recent experiments in polariton chemistry. Intriguing consequences of finite N effects are discussed.

1. J. Yuen-Zhou and A. Koner, Linear response of molecular polaritons, J. Chem. Phys. 160, 154107 (2024).
2. K. Schwennicke and J. Yuen-Zhou, Extracting accurate light–matter couplings from disordered polaritons, Nanophotonics 0049 (2024).
3. J. B. Pérez-Sánchez, A. Koner, N. P Stern, and J. Yuen-Zhou, Simulating molecular polaritons in the collective regime using few-molecule models, Proc. Nat. Acad. Sci. 120(15) e2219223120 (2023).
4. J. Pérez-Sánchez, F. Mellini, N. C. Giebink, and J. Yuen-Zhou, Collective polaritonic effects on chemical dynamics suppressed by disorder, Phys. Rev. Res. 1, 013222 (2024).

Speaker: Joel Yuen-Zhou (UC San Diego)

15:30 Coffee break

37 Optoelectronic strong coupling in plasmon-molecule systems

Metallic nanoparticles support localized surface plasmon resonances (LSPRs) characterized by strongly enhanced local electric fields which amplify physical process occurring in those volumes. These tunable resonances by virtue of modifying the shape and size of the nanoparticle, posses very small mode volumes, greatly amplifying the efficiency of light-matter interactions. We employ real-time TD-DFT simulations to study the metal nanoparticle - organic molecules ensembles in the regimes of weak and strong coupling under electronic excitation.
We investigate how the "macroscopic" changes, i.e. as approximated by the coupled oscillators model, correspond with the "microscopic" changes visible on the level of single Kohn-Sham transitions and their energy shifts. These changes are the result of modifications of the molecular oscillator in the strongly coupled systems, including the resonance energy redshift and widening of the line. These changes correspond with the observed molecular absorption changes, i.e. the initially enhanced absorption is quenched when the molecule and the nanoparticle are placed closer to each other. This can be attributed to purely molecular transitions coupling to the variety of nanoparticle energy states, forming mixed transitions, i.e. occurring when the initial and excited states are located in different subparts of the system. We compare weakly and strongly coupled systems to pinpoint the role of strong coupling in the observed effects and show that, even though mixed transitions can be observed in the weakly coupled systems, their intensity is negligible, as the molecular absorption itself is not enhanced when the molecular transition is detuned from the plasmonic mode. The effects can help tailor the polaritonic states and will be crucial when designing the novel devices based on strong light-matter coupling. Importantly, these changes then transfer into modified hot carrier dynamics in the upper and lower polariton branches, which can be tuned by modifying the interacting entities, their coupling strength, emitter number, etc.

Speaker: Tomasz Antosiewicz (University of Warsaw)

38 Polariton mediated energy transfer through non-Markovian vibrations

The growing field of polariton chemistry calls for a deeper understanding of the role the different vibrational modes play in the system. The ability of low frequency vibrational modes to act as a reservoir of energy to facilitate off-resonant transitions is likely to be relevant in many processes. However, the non-Markovian nature of those modes make them hard to model. One way to capture these effects is using process tensor matrix product operator methods to describe the vibrational environment of the molecules while describing the light using mean-field approximations.
In this talk I will demonstrate the use of this approach to model the energy transfer between different species of molecules that couple to the same cavity photon mode. To do this we look at how the emission spectra of the combined system evolves over time, and how this is affected by the coupling to a continuum of vibrational modes.

Speaker: Kristín Björg Arnardóttir (University of Southern Denmark)