Few-Molecule Strong Coupling with Dimers of Plasmonic Nanoparticles Assembled on DNA

Abstract

Hybrid nanostructures, in which a known number of quantum emitters are strongly coupled to a plasmonic resonator, should feature optical properties at room temperature such as few-photon nonlinearities or coherent superradiant emission. We demonstrate here that this coupling regime can only be reached with dimers of gold nanoparticles in stringent experimental conditions, when the interparticle spacing falls below 2 nm. Using a short transverse DNA double-strand, we introduce 5 dye molecules in the gap between two 40 nm gold particles and actively decrease its length down to sub-2 nm values by screening electrostatic repulsion between the particles at high ionic strengths. Single-nanostructure scattering spectroscopy then evidences the observation of a strong-coupling regime in excellent agreement with electrodynamic simulations. Furthermore, we highlight the influence of the planar facets of polycrystalline gold nanoparticles on the probability of observing strongly coupled hybrid nanostructures.

Theoretical Challenges in Polaritonic Chemistry

“…Effective mode volumes (roughly proportional to the physical volume occupied by the EM mode) can reach below 100 nm 3 51 and possibly even down to ≈1 nm 3 . 52 − 55 Such setups, depicted in Figure 1 b, allow strong coupling to be reached with a few molecules 56 , 57 or even a single emitter. 51 , 58 − 60 …”

“…While such systems are often referred to as (nano)­cavities for simplicity, a more physically accurate nomenclature is “resonator” or “antenna”. Effective mode volumes (roughly proportional to the physical volume occupied by the EM mode) can reach below 100 nm 3 and possibly even down to ≈1 nm 3 . − Such setups, depicted in Figure b, allow strong coupling to be reached with a few molecules , or even a single emitter. ,− …”

“…Effective mode volumes (roughly proportional to the physical volume occupied by the EM mode) can reach below 100 nm 351 and possibly even down to ≈1 nm 3 . 52−55 Such setups, depicted in Figure 1b, allow strong coupling to be reached with a few molecules 56,57 or even a single emitter. 51,58−60 Despite a difference of many orders of magnitude in the effective volume of the modes and the number of involved molecules, typical Rabi splittings (corresponding to the energy difference between the two polariton modes formed when a molecular transition and a cavity mode are on resonance) in both systems are comparable and range from Ω R ≈ 100 meV up to more than an eV.…”

Advanced hybrid plasmonic nano-emitters using smart photopolymer

“…[19][20][21][22] For the structures presenting a gap, including dimers and particles-film structures, DNA origami has proved to be able to place emitters, even a single one, within the gap. [23][24][25][26][27]. In other words, DNA is generally used for both bridging particles together and attaching nano-emitters.…”

Unconventional saturation effects at intermediate drive in a lossy cavity coupled to few emitters

“…[13], proposing a single-photon optical transistor. Lastly, the fact that strong coupling between cavities and emitter ensembles can be observed at room-temperature in these dissipative hybrid systems, motivates the search for observation and possible application of quantum-optical phenomena beyond cryogenic temperatures [68][69][70][71]. This article is organized as follows.…”