Hot Electron Dynamics in Plasmonic Nanostructures

Plasmonic nanostructures concentrate light into subwavelength volumes by exciting collective oscillations of conduction electrons at metal–dielectric interfaces. The rapid decay of these localised surface plasmons generates energetic “hot” electrons and holes far from thermal equilibrium. These carriers undergo a cascade of ultrafast processes—including electron–electron scattering, electron–phonon coupling and energy transfer to adjacent media—that define their lifetimes, energy distributions and eventual harnessing in applications. Understanding these dynamics is crucial for advancing photocatalysis, photodetection, nanoscale optoelectronics and ultrafast optical modulation. Key challenges lie in relating transient optical signals to actual carrier distributions, quantifying injection efficiencies at interfaces and engineering nanostructure morphology and crystallinity to optimise hot‐electron yield and transfer. Recent research has provided new experimental techniques and theoretical models to resolve non‐thermal distributions, measure interfacial injection and tailor relaxation pathways, thereby paving the way for energy‐conversion and ultrafast photonic devices with enhanced performance and selectivity.

Research from Nature Portfolio

Investigations into ultrathin monocrystalline gold films have revealed that crystallinity and interface properties dramatically influence hot‐electron thermalisation. Compared with polycrystalline films, monocrystalline gold exhibits a distinct interplay between non‐thermal and thermal carrier populations, with interband transitions at high‐symmetry points governing intraband relaxation. Experiments show nearly optimal hot‐electron injection into adjacent semiconductor substrates, demonstrating that high crystallinity can push transfer efficiencies close to fundamental limits. A complementary methodological advance applies a double‐inversion procedure to time-resolved pump-probe reflectivity data, directly extracting non-Fermi‐Dirac electron distributions and their thermalisation kinetics. This approach clarifies the ultrafast emergence of non-thermal populations and quantifies plasmon‐induced broadening of energy distributions under different excitation geometries. Furthermore, universal expressions have been derived to capture how electron–electron and electron–phonon interaction strengths jointly govern carrier relaxation timescales, revealing that interelectronic scattering can accelerate phonon emission and that high‐energy state lifetimes depend predominantly on electron–electron couplings, even when phonon scattering is dominant.

Hot Electron Dynamics in Plasmonic Nanostructures publication trend

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

Technical terms

Plasmon: A collective oscillation of free electrons at a metal–dielectric interface induced by incident light.

Hot electron: An electron excited to energies well above the Fermi level, initially out of thermal equilibrium with the lattice.

Electron–electron scattering: Interactions among electrons that redistribute energy and drive an initially non-thermal population towards a quasi-equilibrium distribution.

Electron–phonon coupling: Energy transfer between excited electrons and lattice vibrations, leading to thermalisation of electronic and phononic subsystems.

Thermalisation: The process by which a non-equilibrium electronic distribution relaxes to a Fermi–Dirac distribution characterised by an elevated electron temperature.

References

1. Hot-electron dynamics in plasmonic nanostructures: fundamentals, applications and overlooked aspects. eLight (2024).
2. Ultrafast hot-carrier dynamics in ultrathin monocrystalline gold. Nature Communications (2024).
3. Determining Quasi-Equilibrium Electron and Hole Distributions of Plasmonic Photocatalysts Using Photomodulated X‑ray Absorption Spectroscopy. ACS Nano (2024).
4. Tailored Dispersion of Spectro‐Temporal Dynamics in Hot‐Carrier Plasmonics. Advanced Science (2023).
5. Determination of hot carrier energy distributions from inversion of ultrafast pump-probe reflectivity measurements. Nature Communications (2018).
6. Ultrafast hot electron dynamics in plasmonic nanostructures: experiments, modelling, design. Nanophotonics (2023).
7. Parametric dependence of hot electron relaxation timescales on electron-electron and electron-phonon interaction strengths. Communications Physics (2020).