Tracking ultrafast hot-electron diffusion in space and time by ultrafast thermomodulation microscopy

A. Block, M. Liebel, R. Yu, M. Spector, Y. Sivan, F. J. García De Abajo, N. F. Van Hulst

Research output: Contribution to journalArticlepeer-review

111 Scopus citations

Abstract

The ultrafast response of metals to light is governed by intriguing nonequilibrium dynamics involving the interplay of excited electrons and phonons. The coupling between them leads to nonlinear diffusion behavior on ultrashort time scales. Here, we use scanning ultrafast thermomodulation microscopy to image the spatiotemporal hot-electron diffusion in thin gold films. By tracking local transient reflectivity with 20-nm spatial precision and 0.25-ps temporal resolution, we reveal two distinct diffusion regimes: An initial rapid diffusion during the first few picoseconds, followed by about 100-fold slower diffusion at longer times. We find a slower initial diffusion than previously predicted for purely electronic diffusion. We develop a comprehensive three-dimensional model based on a two-temperature model and evaluation of the thermo-optical response, taking into account the delaying effect of electron-phonon coupling. Our simulations describe well the observed diffusion dynamics and let us identify the two diffusion regimes as hot-electron and phononlimited thermal diffusion, respectively.

Original languageEnglish
Article numbereaav8965
JournalScience advances
Volume5
Issue number5
DOIs
StatePublished - 1 Jan 2019

Keywords

  • Physics - Optics

ASJC Scopus subject areas

  • General

Fingerprint

Dive into the research topics of 'Tracking ultrafast hot-electron diffusion in space and time by ultrafast thermomodulation microscopy'. Together they form a unique fingerprint.

Cite this