Two-Dimensional Plasmonic Phenomena in Electron Systems

Plasmons are collective oscillations of free charge that arise when electrons within a conductor respond coherently to an external electromagnetic field. In two-dimensional electron systems (2DES), such as graphene, semiconductor quantum wells or oxide interfaces, plasmons exhibit a gapless dispersion relation spanning frequencies from the subterahertz to the mid-infrared. The confinement of carriers to a plane leads to enhanced field localisation and tunability via electrostatic gating, dielectric environment or patterned geometries. In laterally confined structures—stripes, disks or metasurfaces—the interplay between radiative and collisional damping gives rise to non-trivial mode lifetimes and quality factors that can be maximised in high-mobility samples. When a perpendicular magnetic field is applied, plasmon modes hybridise with cyclotron motion to form magnetoplasmons, whose spectra open tunable gaps and support polaritonic waveguide modes. Advances in fabrication have enabled on-chip terahertz plasmonic cavities, metamaterial resonators and phase-shifting devices, with potential applications in sensing, wireless communications, spectroscopy and quantum-information platforms. The global effort to harness two-dimensional plasmonics draws upon both theoretical electrodynamic models and time-domain spectroscopic techniques to control plasmon dispersion, damping and coupling to far-field radiation.

Research from Nature Portfolio

Recent studies have developed a complete electromagnetic framework for excitation of terahertz plasmon modes in graphene rectangles, revealing that edge-field effects extend the plasmonic near-field beyond geometric boundaries and induce pronounced red shifts in resonance frequencies. The analysis of absorption cross-section spectra and charge-density distributions under different polarisation and shape conditions has clarified mode dispersion and damping mechanisms. Earlier work introduced a monolithic planar terahertz plasmonic circuit in which photoconductive material is integrated with a high-mobility 2DES. Picosecond pulses injected into the system excite plasmons up to ~400 GHz, and a Schottky gate overlying the 2DES forms a tuneable cavity whose resonances can be electrostatically manipulated, offering direct access to ultrafast confined-electron dynamics.

Two-Dimensional Plasmonic Phenomena in Electron Systems publication trend

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

Technical terms

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

Two-dimensional electron system (2DES): Electron gas confined to motion within a plane.

Dispersion relation: Functional dependence of excitation frequency on its wavevector.

Magnetoplasmon: Plasmon mode modified by an external magnetic field, exhibiting cyclotron coupling.

Plasmon-polariton: Hybrid excitation arising from strong coupling between plasmons and photons or waveguide modes.

Quality factor: Dimensionless measure of resonance sharpness, ratio of stored to dissipated energy.

Electrostatic gating: Control of carrier density or potential landscape via applied voltage.

Edge-field effect: Modification of plasmonic field distribution and resonance due to boundary geometry.

References

1. Complete electromagnetic consideration of plasmon mode excitation in graphene rectangles by incident terahertz wave. Scientific Reports (2024).
2. Excitation, detection and electrostatic manipulation of terahertz-frequency range plasmons in a two-dimensional electron system. Scientific Reports (2015).
3. Two-Dimensional Plasmons in Laterally Confined 2D Electron Systems. Nanomaterials (2023).
4. Magnetoplasmon-Polaritons in a Two-Dimensional Electron System with a Back Gate. JETP Letters (2022).
5. Plasma Excitations in SiGe/Si Quantum Wells. JETP Letters (2023).