Strong Light-Matter Interactions in Plasmonic Nanostructures

The study of strong light–matter interactions in plasmonic nanostructures centres on harnessing confined electromagnetic fields to couple surface plasmons with excitons or quantum emitters. Localised surface plasmons in metal nanoparticles, nanocavities or patterned arrays can confine photons to nanometre volumes far below the diffraction limit, dramatically enhancing optical field strengths. When the coupling rate between plasmons and matter excitations surpasses dissipative losses, hybrid light–matter states (polaritons) emerge, observable through characteristic energy splittings in scattering or absorption spectra. These phenomena can be achieved at room temperature and under ambient conditions, enabling vacuum Rabi splittings of tens to hundreds of millielectronvolts and even ultrastrong coupling regimes. By tuning nanoparticle geometry, inter-particle gaps or integrating two-dimensional materials and molecular emitters, researchers have demonstrated controllable interactions that underpin advances in quantum information processing, ultrafast photonics, low-threshold lasing, sensing and energy harvesting. The global significance of these capabilities extends from on-chip quantum optics to ultrasensitive biosensing and novel light-emitting devices.

Research from Nature Portfolio

Demonstrations of vacuum Rabi splitting in plasmonic cavities have reached the single quantum emitter limit, showing transparency dips in scattering spectra when individual quantum dots couple to silver bowtie structures with coupling rates up to ~120 meV. In complementary work, ultra-compact gold nanogap resonators interfaced with layered WSe₂ achieve strong exciton–plasmon coupling at room temperature, yielding Rabi splittings exceeding 135 meV and evidencing nonlinear excitonic functionalities with preserved quantum efficiencies above 50%. Further, plasmonic nanorod arrays embedded in optical microcavities have entered the ultrastrong coupling regime (g/ω ≈ 0.55) at ambient conditions, with indirect observation of ground-state energy modifications characteristic of ultrastrong light–matter interaction.

Strong Light-Matter Interactions in Plasmonic Nanostructures publication trend

The graph below shows the total number of articles in strong light-matter interactions in plasmonic nanostructures across all publications each year (not limited to Nature Index journals).

Technical terms

Localised surface plasmon resonance (LSPR): Collective oscillation of conduction electrons in a metal nanoparticle excited by light, leading to strong field confinement.

Strong coupling regime: Interaction regime where the light–matter coupling rate exceeds the losses of both modes, producing hybridised states.

Rabi splitting: Energy separation between upper and lower polariton branches in the strong coupling spectrum.

Polaritons: Quasi-particles formed from the coherent mixing of photons with excitons or plasmons.

Ultrastrong coupling: Regime where the coupling strength becomes a significant fraction of the resonant frequency, altering ground-state properties.

References

1. Vacuum Rabi splitting in a plasmonic cavity at the single quantum emitter limit. Nature Communications (2016).
2. Strong-coupling of WSe2 in ultra-compact plasmonic nanocavities at room temperature. Nature Communications (2017).
3. Ultrastrong coupling between nanoparticle plasmons and cavity photons at ambient conditions. Nature Communications (2020).
4. Near-field strong coupling and entanglement of quantum emitters for room-temperature quantum technologies. PhotoniX (2024).
5. Orientation-Dependent Interaction between the Magnetic Plasmons in Gold Nanocups and the Excitons in WS2 Monolayer and Multilayer. ACS Nano (2023).
6. Strong coupling in plasmonic metal nanoparticles. Nano Convergence (2023).