Tracking the surface atomic motion in a coherent phonon oscillation

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 1 g optical phonons. Using a fluence of 4.2 mJ/cm 2 from a 1.55 eV pump laser, we find resulting coherent vibrational amplitude the interlayer spacings order of 1

[1]  A. Gloskovskii,et al.  Suppression of the vacuum space-charge effect in fs-photoemission by a retarding electrostatic front lens. , 2021, The Review of scientific instruments.

[2]  Sunam Kim,et al.  Ultrafast Carrier-Lattice Interactions and Interlayer Modulations of Bi2Se3 by X-ray Free-Electron Laser Diffraction. , 2021, Nano letters.

[3]  Yui Fukatsu,et al.  Time-resolved X-ray photoelectron diffraction using an angle-resolved time-of-flight electron analyzer , 2020, Japanese Journal of Applied Physics.

[4]  G. Cerullo,et al.  Ultrafast spectroscopy: state of the art and open challenges. , 2019, Journal of the American Chemical Society.

[5]  A. Oelsner,et al.  Time- and momentum-resolved photoemission studies using time-of-flight momentum microscopy at a free-electron laser. , 2019, The Review of scientific instruments.

[6]  A. Cavalleri,et al.  Probing dynamics in quantum materials with femtosecond X-rays , 2018, Nature Reviews Materials.

[7]  G. Schönhense,et al.  Multidimensional photoemission spectroscopy—the space-charge limit , 2018 .

[8]  D. Lizzit,et al.  Epitaxial growth of single-orientation high-quality MoS2 monolayers , 2018, 1802.02220.

[9]  Kazutaka G. Nakamura,et al.  Femtosecond study of A1g phonons in the strong 3D topological insulators: From pump-probe to coherent control , 2018, 1801.02551.

[10]  S.-L. Yang,et al.  Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser , 2017, Science.

[11]  A. Lindenberg,et al.  Visualization of Atomic-Scale Motions in Materials via Femtosecond X-Ray Scattering Techniques , 2017 .

[12]  D. Mihailovic,et al.  Ultrafast optical spectroscopy of strongly correlated materials and high-temperature superconductors: a non-equilibrium approach , 2016, 1601.07204.

[13]  G. Schönhense,et al.  Correction of the deterministic part of space-charge interaction in momentum microscopy of charged particles. , 2015, Ultramicroscopy.

[14]  U. Bovensiepen,et al.  Elementary relaxation processes investigated by femtosecond photoelectron spectroscopy of two‐dimensional materials , 2012 .

[15]  Siarhei Dziarzhytski,et al.  The monochromator beamline at FLASH: performance, capabilities and upgrade plans , 2011, 1301.4087.

[16]  Franz Tavella,et al.  The FLASH pump–probe laser system: Setup, characterization and optical beamlines , 2011 .

[17]  Y. P. Chen,et al.  Ultrafast carrier and phonon dynamics in Bi2Se3 crystals , 2010, 1010.4265.

[18]  Wilfried Wurth,et al.  Monochromator beamline for FLASH , 2006 .

[19]  M. Berz,et al.  Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment: Editorial , 2006 .

[20]  S. Hoffmann,et al.  An undulator-based spherical grating monochromator beamline for angle-resolved photoemission spectroscopy , 2004 .

[21]  O. Madelung.  Semiconductors: Data Handbook , 2003 .

[22]  L. Schlapbach,et al.  Angle-scanned photoelectron diffraction , 1995 .

[23]  D. P. Woodruff,et al.  Adsorbate structure determination on surfaces using photoelectron diffraction , 1994 .

[24]  D. P. Woodruff,et al.  Direct identification of atomic and molecular adsorption sites using photoelectron diffraction , 1994, Nature.

[25]  D. P. Woodruff,et al.  Following the changes in local geometry associated with a surface reaction: the dehydrogenation of adsorbed ethylene , 1994 .

[26]  D. R. Penn,et al.  Calculations of electron inelastic mean free paths. III. Data for 15 inorganic compounds over the 50–2000 eV range , 1991 .

[27]  Sebastian Doniach,et al.  Many-electron singularity in X-ray photoemission and X-ray line spectra from metals , 1970 .

[28]  Seizo Nakajima.  The crystal structure of Bi2Te3−xSex , 1963 .

[29]  Peter D. Johnson.  Angle-Resolved Photoemission , 2020, Synchrotron Light Sources and Free-Electron Lasers.

[30]  W. Vanderbauwhede,et al.  Nuclear Instruments and Methods in Physics Research , 2009 .

[31]  Physical Review Letters 63 , 1989 .