2018/09/27 by A. Block, Alexander Block, M. Liebel +11 · 179 citations
Biochemistry, Genetics and Molecular Biology · Materials Science · Physics and Astronomy · #Advanced Electron Microscopy Techniques and Applications #Coupling (piping) #Diffusion #Electron and X-Ray Spectroscopy Techniques #Excited state #Force Microscopy Techniques and Applications #Microscopy #Non-equilibrium thermodynamics #Nonlinear system #Tracking (education) #Transient (computer programming) #Ultrashort pulse #physics.optics
paper · pdf · doi:10.1126/sciadv.aav8965
published in Science Advances 5(5), eaav8965 (American Association for the Advancement of Science) · 20 pages, 8 figures
arxiv created 2018/09/27 · openalex created_date 2018/10/05 · openalex publication_date 2019/05/03 · arxiv updated 2020/08/11 · openalex updated_date 2026/08/05
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 phonon-limited thermal diffusion, respectively.