Direct measurement of anharmonic decay channels of a coherent phonon

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Teitelbaum, Samuel W.
Henighan, Thomas
Huang, Yijing
Liu, Hanzhe
Jiang, Mason P.
Zhu, Diling
Chollet, Matthieu
Sato, Takahiro
Murray, Éamonn D.
Fahy, Stephen B.
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We report channel-resolved measurements of the anharmonic coupling of the coherent A1g 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 A1g frequency that are observed across the Brillouin zone by femtosecond x-ray diffuse scattering. We extract anharmonic coupling constants between the A1g and several representative decay channels that are within an order of magnitude of density functional perturbation theory calculations.
Coherent phonon , Anharmonic coupling , Decay , Temporal oscillations
Teitelbaum, S.W., Henighan, T., Huang, Y., Liu, H., Jiang, M. P., Zhu, D., Chollet, M., Sato, T., Murray, É. D., Fahy, S., O’Mahony, S., Bailey, T. P., Uher, C., Trigo, M. and Reis, D. A. (2018) 'Direct measurement of anharmonic decay channels of a coherent phonon', Physical Review Letters, 121(12), 125901 (6pp). doi:10.1103/PhysRevLett.121.125901
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