Ultrafast Electron Dynamics in Plasmonic Systems

Ultrafast electron dynamics in plasmonic systems merges the physics of collective electron oscillations with the temporal precision of femtosecond and attosecond spectroscopy. When light impinges on a metal–dielectric interface or a metal nanoparticle, it can excite surface plasmon polaritons or localised surface plasmons, respectively. These quasiparticles concentrate electromagnetic energy into nanoscale volumes and create large, transient electric fields. Within femtoseconds, these fields drive non-equilibrium distributions of “hot” electrons, generate coherent polarisation in the metal, and couple to underlying electronic bands. The ensuing processes—dephasing, energy relaxation via electron–electron and electron–phonon interactions, and carrier transport—occur on sub-100-fs to picosecond timescales. Advances in time-resolved photoemission microscopy and spectroscopy have enabled real-space imaging of plasmon wavepackets and direct mapping of hot-electron energy and momentum. Such insights underpin applications ranging from ultrafast switching in nanocircuits and photochemical catalysis to on-chip data processing and quantum light control. The interplay between coherent control of plasmon propagation, energy conversion into hot carriers and the engineering of Floquet-like band structures opens new avenues for manipulating light–matter interactions at the ultimate speed limit.

Research from Nature Portfolio

Recent studies have demonstrated coherent coupling between nano-focused surface plasmon polaritons and distinct electronic states in a metal band structure. By launching intense, polarised plasmon pulses on Au(111), researchers observed above-threshold electron emission from the Shockley surface state, absorbing up to seven plasmon quanta. Time-resolved photoelectron spectroscopy revealed that the process retains quantum coherence akin to strong-field light-matter interactions. This work paves the way for Floquet engineering in plasmonic nanostructures, whereby plasmon fields dynamically reshape electronic bands while preserving coherence against dissipation.

Ultrafast Electron Dynamics in Plasmonic Systems publication trend

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

Technical terms

Surface plasmon polariton (SPP): A coupled excitation of photons and collective electron oscillations propagating along a metal–dielectric interface.

Localised surface plasmon resonance (LSPR): A non-propagating oscillation of conduction electrons confined to metallic nanoparticles or nanostructures.

Hot electrons: Non-equilibrium, high-energy carriers generated by rapid decay of plasmons or direct photon absorption in metals.

Time-resolved photoemission electron microscopy (PEEM): A technique combining ultrafast laser excitation and electron emission imaging to capture nanoscale field dynamics in real time.

Floquet engineering: The modification of electronic band structures through periodic driving with light fields, creating hybrid photon–matter states.

References

1. Few-Cycle Surface Plasmon Polaritons. Nano Letters (2024).
2. High spatiotemporal resolved imaging of ultrafast control of nondiffracting surface plasmon polaritons. Nanophotonics (2023).
3. Focused surface plasmon polaritons coherently couple to electronic states in above-threshold electron emission. Communications Physics (2023).
4. Energy and Momentum Distribution of Surface Plasmon-Induced Hot Carriers Isolated via Spatiotemporal Separation. ACS Nano (2021).