StroCOMP: Strong Coupling of Organic Molecules and Plasmons
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StroCOMP is funded by a Marie Curie Career Integration Grant of the European Union Seventh Framework Programme.

Summary

The improvement of fabrication technology over the last decades enables the accurate creation of almost arbitrarily shaped nanoscale metal structures. In such systems, quasi-bound surface modes (plasmons) provide strong, sub-wavelength confinement of electromagnetic fields. This confinement leads to strongly increased coupling between light and matter, and increases the possible spatial resolution, making it possible to surpass the diffraction limit of conventional optics. These properties make plasmonics a quickly growing and multidisciplinary subject, with applications in physics, chemistry, biology and engineering. A particularly relevant topic is the coupling of quantum emitters (such as atoms, molecules, quantum dots, or color centers in diamond) to plasmons. By concentrating light with the use of plasmons, the mismatch between the absorption cross section of the emitter and the size of the light beam can be circumvented. It is then even possible to reach the strong coupling regime, where the elementary excitations become hybrid states with mixed light-matter character, so called exciton-polaritons. The major aim of StroCOMP is to develop new insights into the strong coupling between plasmons and organic molecule excitation. Due to the complex molecular structure, organic molecule exciton-polaritons are still not fully understood. A further goal of the project is to study the manipulation of chemical structure and reactions through strong coupling, exploiting the modification of the chemical potential energy surface.

People

Johannes Dr. Johannes Feist
Marie Curie CIG Research Fellow
johannes.feist@uam.es

Departamento de Física Teórica de la Materia Condensada
Facultad de Ciencias, Module C-05, 503
Universidad Autónoma de Madrid
Tel.: +34 91497 2662
FJ Prof. Francisco J. García Vidal
Scientific coordinator
fj.garcia@uam.es

Departamento de Física Teórica de la Materia Condensada
Facultad de Ciencias, Module C-05, 401.2
Universidad Autónoma de Madrid
Tel.: +34 91497 8515
Javier Javier Galego Pascual
PhD student
javier.galego@uam.es

Departamento de Física Teórica de la Materia Condensada
Facultad de Ciencias, Module C-05, 305
Universidad Autónoma de Madrid

Publications

Publications financially supported by StroCOMP:

2017

13.
Multiscale Molecular Dynamics Simulations of Polaritonic Chemistry (PDF)
H. L. Luk, J. Feist, J. J. Toppari, and G. Groenhof
Abstract: ...When photoactive molecules interact strongly with confined light modes as found in plasmonic structures or optical cavities, new hybrid light-matter states can form, the so-called polaritons. These polaritons are coherent superpositions (in the quantum mechanical sense) of excitations of the molecules and of the cavity photon or surface plasmon. Recent experimental and theoretical works suggest that access to these polaritons in cavities could provide a totally new and attractive paradigm for controlling chemical reactions that falls in between traditional chemical catalysis and coherent laser control. However, designing cavity parameters to control chemistry requires a theoretical model with which the effect of the light-matter coupling on the molecular dynamics can be predicted accurately. Here we present a multiscale quantum mechanics/molecular mechanics (QM/ MM) molecular dynamics simulation model for photoactive molecules that are strongly coupled to confined light in optical cavities or surface plasmons. Using this model we have performed simulations with up to 1600 Rhodamine molecules in a cavity. The results of these simulations reveal that the contributions of the molecules to the polariton are time-dependent due to thermal fluctuations that break symmetry. Furthermore, the simulations suggest that in addition to the cavity quality factor, also the Stokes shift and number of molecules control the lifetime of the polariton. Because large numbers of molecules interacting with confined light can now be simulated in atomic detail, we anticipate that our method will lead to a better understanding of the effects of strong coupling on chemical reactivity. Ultimately the method may even be used to systematically design cavities to control photochemistry.
11.
Plasmon-exciton-polariton lasing (PDF)
M. Ramezani, A. Halpin, A. I. Fernández-Domínguez, J. Feist, S. R.-K. Rodriguez, F. J. Garcia-Vidal, and J. Gómez Rivas
Abstract: ...Metallic nanostructures provide a toolkit for the generation of coherent light below the diffraction limit. Plasmonic-based lasing relies on the population inversion of emitters (such as organic fluorophores) along with feedback provided by plasmonic resonances. In this regime, known as weak light–matter coupling, the radiative characteristics of the system can be described by the Purcell effect. Strong light–matter coupling between the molecular excitons and electromagnetic field generated by the plasmonic structures leads to the formation of hybrid quasi-particles known as plasmon-exciton-polaritons (PEPs). Due to the bosonic character of these quasi-particles, exciton-polariton condensation can lead to laser-like emission at much lower threshold powers than in conventional photon lasers. Here, we observe PEP lasing through a dark plasmonic mode in an array of metallic nanoparticles with a low threshold in an optically pumped organic system. Interestingly, the threshold power of the lasing is reduced by increasing the degree of light–matter coupling in spite of the degradation of the quantum efficiency of the active material, highlighting the ultrafast dynamic responsible for the lasing, i.e., stimulated scattering. These results demonstrate a unique room-temperature platform for exploring the physics of exciton-polaritons in an open-cavity architecture and pave the road toward the integration of this on-chip lasing device with the current photonics and active metamaterial planar technologies.

2016

2015

5.
Radiative heat transfer in the extreme near field (PDF)
K. Kim, B. Song, V. Fernández-Hurtado, W. Lee, W. Jeong, L. Cui, D. Thompson, J. Feist, M. T. H. Reid, F. J. García-Vidal, J. C. Cuevas, E. Meyhofer, and P. Reddy
Abstract: ...Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres, quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.