Plasmonic Properties in Graphene and Two-Dimensional Materials

Graphene and related atomically thin crystals support plasmons—collective oscillations of electrons that propagate along a two-dimensional plane. In graphene, the linear band structure near the Dirac point gives rise to so-called Dirac plasmons whose frequency scales as the square root of in-plane wavevector, differing fundamentally from conventional two-dimensional electron gases. Reduced dimensionality and broken translational symmetry in quasi-2D metals yield nearly dispersionless “slow” plasmons, which combine long lifetimes with field-enhancement factors exceeding 10⁷ and localisation to tens of nanometres. Doping, gating and the choice of substrate or encapsulating layers tune plasmon energy and propagation length, enabling active control of resonance frequency in the mid-infrared to terahertz regimes. Heterostructures formed by stacking graphene with hexagonal boron nitride or transition metal dichalcogenides introduce strong exciton–plasmon hybridisation, while arrays of nanoribbons and patterned architectures permit edge-guided modes and engineered dispersion. Acoustic plasmons, emerging from anisotropic carrier dynamics or multi-carrier coexistence, offer linear dispersion at long wavelengths. Recent advances in momentum-resolved spectroscopy and scattering-type near-field optical microscopy have mapped plasmon dispersion across the Brillouin zone, revealing the influence of interband screening, local-field effects and structural modulation. These phenomena underpin applications in compact photonic circuits, sensitive biosensing platforms and real-time plasmon imaging, marking a transformative frontier in two-dimensional optoelectronics and nanophotonics.

Research from Nature Portfolio

Recent studies have shown that plasmons in atomically thin quasi-2D metals are intrinsically dispersionless for experimentally relevant wavevectors due to interband screening arising from broken continuous symmetry. Ab initio calculations reveal that monolayer metallic transition metal dichalcogenides support tunable, long-lived plasmons capable of extreme field enhancement and real-space localisation within ~20 nm, opening routes to track plasmon wave packets in real time. Complementary work on monolayer germanene has identified multiple plasmon modes—including two-dimensional acoustic modes at long wavelength—whose existence and behaviour depend sensitively on spin–orbit coupling, gate voltage and momentum direction, illustrating the richness of plasmonic phenomena beyond graphene.

Plasmonic Properties in Graphene and Two-Dimensional Materials publication trend

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

Technical terms

Plasmon: A quantised collective oscillation of conduction electrons in a material, often coupled to an electromagnetic field.

Dirac plasmon: A plasmon in graphene arising from its linear electronic dispersion near the Dirac point, with frequency ω∝√q.

Acoustic plasmon: A low-energy plasmon mode exhibiting linear dispersion at long wavelengths, typically arising from multi-carrier or anisotropic band structures.

Dispersion relation: The functional dependence of a mode’s frequency on its wavevector, characterising propagation and confinement.

Heterostructure: A layered assembly of two or more different two-dimensional materials held together by van der Waals forces.

Exciton: A bound state of an electron and a hole in a semiconductor or insulator, which can couple to plasmons to form hybrid modes.

References

1. Universal slow plasmons and giant field enhancement in atomically thin quasi-two-dimensional metals. Nature Communications (2020).
2. Tunable plasmons in regular planar arrays of graphene nanoribbons with armchair and zigzag-shaped edges. Beilstein Journal of Nanotechnology (2017).
3. Proving Surface Plasmons in Graphene Nanoribbons Organized as 2D Periodic Arrays and Potential Applications in Biosensors. Chemosensors (2022).
4. Mapping the energy-momentum dispersion of hBN excitons and hybrid plasmons in hBN-WSe2 heterostructures. npj 2D Materials and Applications (2024).
5. Optically driven plasmons in graphene/hBN van der Waals heterostructures: simulating s-SNOM measurements. Nanophotonics (2024).
6. Coulomb excitations of monolayer germanene. Scientific Reports (2017).
7. Acoustic plasmons in extrinsic free-standing graphene. New Journal of Physics (2014).