Quantum electrodynamics at room temperature coupling a single vibrating molecule with a plasmonic nanocavity

Abstract

Interactions between a single emitter and cavity provide the archetypical system for fundamental quantum electrodynamics. Here we show that a single molecule of Atto647 aligned using DNA origami interacts coherently with a sub-wavelength plasmonic nanocavity, approaching the cooperative regime even at room temperature. Power-dependent pulsed excitation reveals Rabi oscillations, arising from the coupling of the oscillating electric field between the ground and excited states. The observed single-molecule fluorescent emission is split into two modes resulting from anti-crossing with the plasmonic mode, indicating the molecule is strongly coupled to the cavity. The second-order correlation function of the photon emission statistics is found to be pump wavelength dependent, varying from g (2) (0) = 0.4 to 1.45, highlighting the influence of vibrational relaxation on the Jaynes-Cummings ladder. Our results show that cavity quantum electrodynamic effects can be observed in molecular systems at ambient conditions, opening significant potential for device applications.

Nano‐Cavity QED with Tunable Nano‐Tip Interaction

“…The ability to precisely control the relative cavity–emitter position in TESC enables large single‐emitter coupling strengths of meV that are comparable even to those achieved using large ensembles of emitters, and are significantly larger than those seen in other experiments which use DNA origami and configurable cavity designs to improve the coupling strength by controlling the position of an emitter within the cavity . By combining this ability to precisely control the experimental geometry on the single‐nanometer scale, with electromagnetic simulations of the cavity field, we also gain insight into the dynamics of cavity formation as the tip‐emitter‐substrate geometry is varied in a well‐defined manner.…”

“…In these systems, low temperature operation is generally required to sufficiently decouple emitters from their environment and reduce their dephasing rate below that of the cavity–emitter coupling strength. However, a new regime of strong cavity–emitter interaction has recently been established using plasmonic nano‐cavities with deep sub‐diffraction‐limited mode volumes . While plasmonic nanocavities extend quantum state control even to room temperature, this approach has relied largely on nano‐fabrication techniques to generate static plasmonic cavities, which limit the ability to tune, control, and image emitters in the strong coupling regime.…”

“…Recently, plasmonic nano‐antenna cavities in the form of highly polarizable metallic nanostructures with dimensions down to just a few nanometers, which allow for deep sub‐diffraction limited mode volumes, have been broadly employed to generate hybrid quantum states of plasmons and emitters . The increased interaction rate facilitated by these nanoscopic cavity mode volumes have enabled strong coupling to both ensembles and single emitters at room temperature …”

“…Over the past two years, strongly coupled plexciton states were observed in the emission of single emitters coupled to plasmonic cavities in several experiments at room temperature. Most of these employed nanoparticle‐on‐a‐mirror (NPoM) geometry in which an emitter is located between a metal nanoparticle and a planar metal substrate . This is a significant landmark for the field, as this modality provides unambiguous evidence of strong coupling and paves the way for new applications in single emitter quantum information and photonic quantum devices.…”

“…However, while significant progress has been made in extending single emitter strong coupling to scalable, room temperature platforms based on plasmonic nano‐cavities with deep sub‐diffraction‐limited mode volumes, this approach has focused primarily on the fabrication and implementation of static plasmonic cavities, which do not allow for imaging, optimization, or control of the spatially dependent cavity–emitter interaction strength. Indeed, recent work on a quantum dot coupled to a scanning plasmonic slot structure suggests evidence for reaching the strong coupling regime in single emitter PL at room temperature, yet is plagued by convoluted spectra with large background and competing artefacts due to charged exciton emission.…”