# Pump-probe Spectroscopy Study of Ultrafast Temperature Dynamics in Nanoporous Gold

## TL;DR

This study investigates how nanoporous gold structures affect ultrafast electron temperature dynamics, revealing slower relaxation and higher peak electron temperatures, with implications for thermal control in nanostructured metals.

## Contribution

It demonstrates that nanoporous geometry significantly influences electron-lattice relaxation times and peak electron temperatures, advancing understanding of ultrafast thermal processes in nanostructured metals.

## Key findings

- Nanoporous gold slows electron-lattice relaxation.
- Higher peak electron temperatures in nanoporous gold.
- Electron-phonon coupling scales with metal filling factor.

## Abstract

We explore the influence of the nanoporous structure on the thermal relaxation of electrons and holes excited by ultrashort laser pulses ($\sim 7$ fs) in thin gold films. Plasmon decay into hot electron-hole pairs results in the generation of a Fermi-Dirac distribution thermalized at a temperature $T_{\mathrm{e}}$ higher than the lattice temperature $T_{\mathrm{l}}$. The relaxation times of the energy exchange between electrons and lattice, here measured by pump-probe spectroscopy, is slowed down by the nanoporous structure, resulting in much higher peak $T_{\mathrm{e}}$ than for bulk gold films. The electron-phonon coupling constant and the Debye temperature are found to scale with the metal filling factor $f$ and a two-temperature model reproduces the data. The results open the way for electron temperature control in metals by engineering of the nanoporous geometry.