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Decelerated lattice excitation and absence of bulk phonon modes at surfaces: Ultra-fast electron diffraction from Bi(111) surface upon fs-laser excitation

Ultrafast reflection high-energy electron diffraction is employed to follow the lattice excitation of a Bi(111) surface upon irradiation with a femtosecond laser pulse. The thermal motion of the atoms is analyzed through the Debye–Waller effect. While the Bi bulk is heated on time scales of 2 to 4 p...

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Bibliographic Details
Published in:Structural dynamics (Melville, N.Y.) N.Y.), 2019-11, Vol.6 (6), p.065101-065101
Main Authors: Tinnemann, V., Streubühr, C., Hafke, B., Witte, T., Kalus, A., Hanisch-Blicharski, A., Ligges, M., Zhou, P., von der Linde, D., Bovensiepen, U., Horn-von Hoegen, M.
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Language:English
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Summary:Ultrafast reflection high-energy electron diffraction is employed to follow the lattice excitation of a Bi(111) surface upon irradiation with a femtosecond laser pulse. The thermal motion of the atoms is analyzed through the Debye–Waller effect. While the Bi bulk is heated on time scales of 2 to 4 ps, we observe that the excitation of vibrational motion of the surface atoms occurs much slower with a time constant of 12 ps. This transient nonequilibrium situation is attributed to the weak coupling between bulk and surface phonon modes which hampers the energy flow between the two subsystems. From the absence of a fast component in the transient diffraction intensity, it is in addition concluded that truncated bulk phonon modes are absent at the surface.
ISSN:2329-7778
2329-7778
DOI:10.1063/1.5128275