"Direct Measurement of Anharmonic Decay Channels of a Coherent Phonon"

Samuel W. Teitelbaum: Thomas Henighan, Yijing Huang, Hanzhe Liu, Mason P. Jiang, Diling Zhu, Matthieu Chollet, Takahiro Sato, Éamonn D. Murray, Stephen Fahy, Shane O’Mahony, Trevor P. Bailey, Ctirad Uher, Mariano Trigo, and David A. Reis; Physical Review Letters, 09/20/18.

Additional Authors: Thomas Henighan, Yijing Huang, Hanzhe Liu, Mason P. Jiang, Diling Zhu, Matthieu Chollet, Takahiro Sato, Éamonn D. Murray, Stephen Fahy, Shane O’Mahony, Trevor P. Bailey, Ctirad Uher, Mariano Trigo, and David A. Reis

Abstract:

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.