Abstract
We report channel-resolved measurements of the anharmonic coupling of the coherent phonon in photoexcited bismuth to pairs of high wave vector acoustic phonons. The decay of a coherent phonon can be understood as a parametric resonance process whereby the atomic displacement periodically modulates the frequency of a broad continuum of modes. This coupling drives temporal oscillations in the phonon mean-square displacements at the frequency that are observed across the Brillouin zone by femtosecond x-ray diffuse scattering. We extract anharmonic coupling constants between the and several representative decay channels that are within an order of magnitude of density functional perturbation theory calculations.
- Received 9 October 2017
- Revised 21 February 2018
DOI:https://doi.org/10.1103/PhysRevLett.121.125901
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