Regensburg 2019 – wissenschaftliches Programm
O 95.2: Vortrag
Freitag, 5. April 2019, 10:45–11:00, H14
Coherent control of the structural phase transition in In-nanowires on Si(111) — •Jan Gerrit Horstmann, Bareld Wit, Gero Storeck, and Claus Ropers — IV. Physical Institute, University of Göttingen, Friedrich-Hund-Platz 1, Germany
Metallic nanowires have become a model system for studying correlation effects and light-matter interaction on the atomic scale, providing access to phenomena such as anisotropic conductivity, long-range spin-order or Peierls transitions. Due to their low dimensionality, these systems exhibit a comparatively small number of structural modes, potentially resulting in long dephasing times of optically-excited coherent phonons. Recently, it was shown that single intense light pulses can drive the surface-specific structural phase transition between the insulating (8×2) and the metallic (4×1) phase of In-nanowires on Si(111) in the limit of critically damped atomic motion . Here, we report the coherent control of this structural phase transition enabled by excitation with optical pulse pairs, thereby demonstrating and harnessing pronounced vibrational coherences in the system. A detailed analysis of the phase transition efficiency as a function of the two-pulse delay recorded by ultrafast low-energy electron diffraction (ULEED)  proves the critical role of two specific phonon modes for the transition , and allows for unique insights to the underlying reaction pathways of this structural phase transition.
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