Polaritonic Chemistry with Organic Molecules (PDF)
Abstract: ...We present an overview of the general concepts of polaritonic chemistry with organic molecules, i.e., the manipulation of chemical structure that can be achieved through strong coupling between confined light modes and organic molecules. Strong coupling and the associated formation of polaritons, hybrid light-matter excitations, leads to energy shifts in such systems that can amount to a large fraction of the uncoupled transition energy. This has recently been shown to significantly alter the chemical structure of the coupled molecules, which opens the possibility to manipulate and control reactions. We discuss the current state of theory for describing these changes and present several applications, with a particular focus on the collective effects observed when many molecules are involved in strong coupling.
Dispersion Anisotropy of Plasmon–Exciton–Polaritons in Lattices of Metallic Nanoparticles (PDF)
Abstract: ...When the electromagnetic modes supported by plasmonic-based cavities interact strongly with molecules located within the cavity, new hybrid states known as plasmon-exciton-polaritons (PEPs) are formed. The properties of PEPs, such as group velocity, effective mass and lifetime, depend on the dispersive and spectral characteristics of the optical modes underlying the strong coupling. In this work, we focus on lattice modes supported by rectangular arrays of plasmonic nanoparticles known as surface lattice resonances (SLRs). We show that SLRs arising from different in-plane diffraction orders in the lattice can couple with the molecular excitons leading to PEPs with distinct dispersions, and thus different group velocities. These results illustrate the possibility of tailoring the transport of PEPs through the design of lattices of plasmonic particles.
Super-Planckian far-field radiative heat transfer (PDF)
Abstract: ...We present here a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. To guide the search for super-Planckian far-field radiative heat transfer, we make use of the theory of fluctuational electrodynamics and derive a relation between the far-field radiative heat transfer and the directional absorption efficiency of the objects involved. Guided by this relation, and making use of state-of-the-art numerical simulations, we show that the far-field radiative heat transfer between highly anisotropic objects can largely overcome the black-body limit when some of their dimensions are smaller than the thermal wavelength. In particular, we illustrate this phenomenon in the case of suspended pads made of polar dielectrics like SiN or SiO2 . These structures are widely used to measure the thermal transport through nanowires and low-dimensional systems and can be employed to test our predictions. Our work illustrates the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nanodevices.
Enhancing photon correlations through plasmonic strong coupling (PDF)
Abstract: ...There is an increasing scientific and technological interest in the design and implementation of nanoscale sources of quantum light. Here, we investigate the quantum statistics of the light scattered from a plasmonic nanocavity coupled to a mesoscopic ensemble of emitters under low coherent pumping. We present an analytical description of the intensity correlations taking place in these systems and unveil the fingerprint of plasmon-exciton-polaritons in them. Our findings reveal that plasmonic cavities are able to retain and enhance excitonic nonlinearities, even when the number of emitters is large. This makes plasmonic strong coupling a promising route for generating nonclassical light beyond the single-emitter level.
Long-distance operator for energy transfer (PDF)
Abstract: ...Nonradiative energy transfer is a ubiquitous phenomenon in nature. Photosynthesis begins with light harvesting, where pigment-protein complexes transform sunlight into excitations, usually called excitons, within the molecules. Excitons are formed by an excited electron and the positively charged hole that is left in the ground state. In photosynthesis, the energy of this exciton is finally transferred to the reaction center, where a charge separation process provides chemical energy for plants, algae, and bacteria. Human-made organic photovoltaic cells try to mimic this natural process, and it is the transport of the excitons after light absorption that determines the efficiency of the cell. In organic materials, energy transfer is governed by short-range dipole-dipole interactions through the process of Förster resonance energy transfer (FRET), whose spatial range is limited to distances less than 10 nm. Recent work by Zhong et al. shows how this range can be extended to distances larger than 100 nm by taking advantage of a quantum electrodynamics (QED) phenomenon called strong coupling.
Many-Molecule Reaction Triggered by a Single Photon in Polaritonic Chemistry (PDF)
Abstract: ...The second law of photochemistry states that in most cases, no more than one molecule is activated for an excited-state reaction for each photon absorbed by a collection of molecules. In this work, we demonstrate that it is possible to trigger a many-molecule reaction using only one photon by strongly coupling the molecular ensemble to a confined light mode. The collective nature of the resulting hybrid states of the system (the so-called polaritons) leads to the formation of a polaritonic "supermolecule" involving the degrees of freedom of all molecules, opening a reaction path on which all involved molecules undergo a chemical transformation. We theoretically investigate the system conditions for this effect to take place and be enhanced.