Ultrastrong coupling in single plexcitonic nanocubes

Abstract

Light-matter strong coupling is defined when the coupling strength exceeds the losses in the system, whereas ultrastrong coupling is not simply strong coupling with even larger coupling strength. Instead, ultrastrong coupling regime arises when the coupling strength is comparable to the transition frequency in the system. At present, ultrastrong light-matter interactions have been achieved in superconducting circuits, semiconductor polaritons, and organic molecules, where these systems are typically at the micrometer scale. In this work, we investigated ultrastrong coupling in a nanoparticle plexcitonic system, i.e. a single gold nanocube coated with quantum emitters and positioned on a gold film. We observed a normalized coupling rate η ~ 0.12 to the antenna mode in such coated nanocube-on-mirror (c-NCoM) configuration at the multilayer emitter level. In contrast to the gap mode that squeezes all the optical fields into the gap region, the antenna mode in c-NCoM provides multiple exterior hot spots at the upper corners of the nanocube, which can be exploited for qubit entanglement within a single nanocube. The concurrence between adjacent emitters is estimated up to 0.6. This theoretical study establishes a promising route toward building a scalable quantum network using single plexcitonic nanocubes as quantum nodes.

Water Oxidation under Modal Ultrastrong Coupling Conditions Using Gold/Silver Alloy Nanoparticles and Fabry–Pérot Nanocavities

“…The absorption spectra showed two peaks attributed to two new hybrid modes (P + , P ‐ ) due to the formation of strong coupling between the LSPR and cavity modes. A third component was also observed in Figure 1 d and was attributed to the uncoupled FP cavity mode [36] . The dispersion curve was generated by plotting the energy of P + and P ‐ as a function of the cavity wavenumber, as shown in Figure 1 e.…”

“…A third component was also observed in Figure 1 d and was attributed to the uncoupled FP cavity mode. [36] The dispersion curve was generated by plotting the energy of P + and P ‐ as a function of the cavity wavenumber, as shown in Figure 1 e . The splitting energy ħΩ was calculated to be 620 meV by using a coupled harmonic oscillator model, as described by Equation (2), and this value was almost twice that determined for ATA with an average size of 12 nm in previous research.…”

Water Oxidation under Modal Ultrastrong Coupling Conditions Using Gold/Silver Alloy Nanoparticles and Fabry–Pérot Nanocavities

“…A third component was also observed in Figure 1 d and was attributed to the uncoupled FP cavity mode. [36] The dispersion curve was generated by plotting the energy of P + and Pas a function of the cavity wavenumber, as shown in Figure 1 e. The splitting energy " hW was calculated to be 620 meV by using a coupled harmonic oscillator model, as described by Equation (2), and this value was almost twice that determined for ATA with an average size of 12 nm in previous research. [20]…”

Controlling plexcitonic strong coupling via multidimensional hotspot nanoengineering

“…[5][6][7] The intense electromagnetic field confinement provided by plasmonic nanocavities compensates for the severe Ohmic loss in metals and enables rapid energy exchange between plasmon polaritons and matter excitons, giving rise to hybrid plasmon-excitons or plexcitons. [8][9][10] Strongly-coupled plexcitonic systems allow for a wide range of applications including ultrafast single-photon emission, 11 single-qubit coherent control, 12 charge transport, 13 long-range energy transfer, 14,15 and universal quantum logic gates, 16 which provide fundamental building blocks for optical communication and quantum information processing. In the context of polariton chemistry, plexcitonic systems can efficiently trigger many-molecule reactions 17 and alter photochemical processes.…”