Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 95: Semiconductor Substrates: Metallic Nanowires

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 [1]. 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) [2] proves the critical role of two specific phonon modes for the transition [3], and allows for unique insights to the underlying reaction pathways of this structural phase transition.

[1] T. Frigge et al., Nature 544, 207-211 (2017). [2] S. Vogelgesang et al., Nat. Physics 14, 184-190 (2018). [3] S. Wippermann et al., PRL 105, 126102 (2010).