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arXiv · 2205.13212

Tracking the surface atomic motion in a coherent phonon oscillation

Davide Curcio·Klara Volckaert·Dmytro Kutnyakhov·Steinn Ymir Agustsson·Kevin Bühlmann·Federico Pressacco·Michael Heber·Siarhei Dziarzhytski·Yves Acremann·Jure Demsar·Wilfried Wurth·Charlotte E. Sanders·Philip Hofmann
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Abstract

X-ray photoelectron diffraction is a powerful tool for determining the structure of clean and adsorbate-covered surfaces. Extending the technique into the ultrafast time domain will open the door to studies as diverse as the direct determination of the electron-phonon coupling strength in solids and the mapping of atomic motion in surface chemical reactions. Here we demonstrate time-resolved photoelectron diffraction using ultrashort soft X-ray pulses from the free electron laser FLASH. We collect Se 3d photoelectron diffraction patterns over a wide angular range from optically excited Bi$_2$Se$_3$ with a time resolution of 140 fs. Combining these with multiple scattering simulations allows us to track the motion of near-surface atoms within the first 3 ps after triggering a coherent vibration of the A$_{1g}$ optical phonons. Using a fluence of 4.2 mJ/cm$^2$ from a 1.55 eV pump laser, we find the resulting coherent vibrational amplitude in the first two interlayer spacings to be on the order of 1 pm.

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Davide Curcio, Klara Volckaert, Dmytro Kutnyakhov, Steinn Ymir Agustsson, Kevin Bühlmann, Federico Pressacco, Michael Heber, Siarhei Dziarzhytski, Yves Acremann, Jure Demsar, Wilfried Wurth, Charlotte E. Sanders, Philip Hofmann. 2022-05-26. Tracking the surface atomic motion in a coherent phonon oscillation. https://doi.org/10.1103/physrevb.106.l201409

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