Plasmonic Excitations in Two-Dimensional Materials

Plasmonic excitations in atomically thin crystals arise from collective oscillations of charge carriers confined within two-dimensional lattices. In materials such as graphene, transition metal dichalcogenides and silicene, reduced dimensionality enhances field confinement and enables resonances at terahertz to visible frequencies. Confinement also yields strong light–matter coupling, opening routes to ultra-compact sensors, modulators and photonic circuits. Plasmon modes in two-dimensional systems may be categorised as localized or propagating surface plasmons, and can hybridise with optical phonons, excitons or substrate modes. Their dispersion and damping are tunable via electrostatic gating, chemical doping, layer number and dielectric environment. Experimentally, electron energy-loss spectroscopy, near-field optical microscopy and terahertz time-domain spectroscopy have elucidated plasmon lifetimes, dispersion relations and nonlocal effects. Theoretically, random-phase approximation, tight-binding models and first-principles calculations provide predictive insight into the role of many-body screening, interband transitions and band-gap engineering. Collectively, these advances underscore the global significance of two-dimensional plasmonics for biosensing, energy harvesting and high-speed optoelectronics.

Research from Nature Portfolio

Recent studies have predicted and characterised hybrid plasmon modes in multilayer graphene coupled to a conducting substrate. A derived dispersion function captures the interplay between graphene’s polarisation and the underlying electron liquid. This work reveals a low-frequency surface plasmon-polariton that lies below the substrate’s bulk plasmon continuum, exhibits negligible damping by particle-hole excitations and is highly sensitive to the layer-to-surface separation, the graphene band gap and the number of layers. Notably, when the layer count exceeds a critical threshold, the hybrid surface plasmon vanishes, demonstrating a route to engineer or suppress specific collective modes by structural design.

Plasmonic Excitations in Two-Dimensional Materials publication trend

The graph below shows the total number of articles in plasmonic excitations in two-dimensional materials across all publications each year (not limited to Nature Index journals).

Technical terms

Plasmon: Collective oscillation of free electron density in a material.

Surface plasmon-polariton: Electromagnetic wave coupled to charge oscillations at a conductor–dielectric interface.

Random-phase approximation (RPA): Theoretical framework that treats many-body electron interactions to predict collective excitations.

Dispersion relation: Functional relationship between the frequency and wavevector of a propagating mode.

Coulomb coupling: Electrostatic interaction between charge carriers in spatially separated layers.

References

1. Plasmon Excitations of Multi-layer Graphene on a Conducting Substrate. Scientific Reports (2016).
2. Temperature-dependent Coulomb excitations in silicene. New Journal of Physics (2014).
3. Plasmon Damping Rates in Coulomb-Coupled 2D Layers in a Heterostructure. Materials (2022).
4. Plasmon modes in bilayer graphene at finite temperature. Science and Technology Development Journal - Natural Sciences (2021).