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arXiv · 1212.2348

Direct observation of non-fully-symmetric coherent optical phonons by femtosecond x-ray diffraction

S. L. Johnson·P. Beaud·E. Möhr-Vorobeva·A. Caviezel·G. Ingold·C. J. Milne
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Abstract

We directly measure by femtosecond time-resolved x-ray diffraction the E$_g$ symmetry coherent phonon excited in bismuth by strong optical excitation. The magnitude of the E$_g$ mode observed is 0.2 pm peak-to-peak, compared against the 2.7 pm initial displacement of the fully-symmetric A$_{1g}$ mode. The much smaller motion of the E$_g$ mode is a consequence of the short lifetime of the electronic states that drive the atomic motion. The experimentally measured magnitude of the E$_g$ motion allows us to rule out a previously suggested scenario for explaining the dynamics in bismuth that relies on strong coupling between these modes.

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S. L. Johnson, P. Beaud, E. Möhr-Vorobeva, A. Caviezel, G. Ingold, C. J. Milne. 2012-12-11. Direct observation of non-fully-symmetric coherent optical phonons by femtosecond x-ray diffraction. https://doi.org/10.1103/physrevb.87.054301

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