# Ultrafast transport and relaxation of hot plasmonic electrons in metal-dielectric heterostructures

## TL;DR

This paper investigates ultrafast electron dynamics in metal-dielectric heterostructures excited by surface plasmon-polaritons, revealing enhanced hot electron generation and slowed relaxation at resonance, with implications for photonics and spintronics.

## Contribution

It develops a kinetic model including local and non-local electron relaxation, extending non-equilibrium dynamics to collective electronic excitations in plasmonic structures.

## Key findings

- Enhanced hot electron generation efficiency by an order of magnitude at SP resonance
- Fourfold slowdown of non-local electron relaxation up to 200 fs
- Experimental validation through pump-probe measurements with varied parameters

## Abstract

We analyze ultrafast electron dynamics in the time domain upon optical excitation of propagating surface plasmon-polaritons (SPs) in metal-dielectric heterostructures. Developing a kinetic model where both local and non-local electron relaxation in metals are included, we identify relevant timescales and extend the existing non-equilibrium electron dynamics framework onto the case of collective electronic excitations. The experimental data obtained in two distinct series of pump-probe measurements (with varied pump wavelength and angle of incidence) demonstrate SP-driven, one order of magnitude enhanced efficiency of the hot electron generation and the fourfold (up to 200 fs) slowdown of their non-local relaxation at the SP resonance. We discuss the perspectives of the SP-enabled manipulation of the non-equilibrium electron population lying at the crossover of photonics and ultrafast spintronics.