Heterodyne x-ray diffuse scattering from coherent phonons

M Kozina; M Trigo; M Chollet; J N Clark; J M Glownia; A C Gossard; T Henighan; M P Jiang; H Lu; A Majumdar; D Zhu; D A Reis

doi:10.1063/1.4989401

Heterodyne x-ray diffuse scattering from coherent phonons

Struct Dyn. 2017 Aug 10;4(5):054305. doi: 10.1063/1.4989401. eCollection 2017 Sep.

Authors

M Kozina, M Trigo, M Chollet¹, J N Clark², J M Glownia¹, A C Gossard³, T Henighan, M P Jiang, H Lu³, A Majumdar, D Zhu¹, D A Reis

Affiliations

¹ Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
² Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
³ Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, USA.

Abstract

Here, we report Fourier-transform inelastic x-ray scattering measurements of photoexcited GaAs with embedded ErAs nanoparticles. We observe temporal oscillations in the x-ray scattering intensity, which we attribute to inelastic scattering from coherent acoustic phonons. Unlike in thermal equilibrium, where inelastic x-ray scattering is proportional to the phonon occupation, we show that the scattering is proportional to the phonon amplitude for coherent states. The wavevectors of the observed phonons extend beyond the excitation wavevector. The nanoparticles break the discrete translational symmetry of the lattice, enabling the generation of large wavevector coherent phonons. Elastic scattering of x-ray photons from the nanoparticles provides a reference for heterodyne mixing, yielding signals proportional to the phonon amplitude.