Kozina M, Trigo M, Chollet M, Clark J N, Glownia J M, Gossard A C, Henighan T, Jiang M P, Lu H, Majumdar A, Zhu D, Reis D A
Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Struct Dyn. 2017 Aug 10;4(5):054305. doi: 10.1063/1.4989401. eCollection 2017 Sep.
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.
在此，我们报告了对嵌入ErAs纳米颗粒的光激发GaAs进行的傅里叶变换非弹性X射线散射测量。我们观察到X射线散射强度的时间振荡，将其归因于来自相干声子的非弹性散射。与热平衡状态下不同，在热平衡中，非弹性X射线散射与声子占据数成正比，我们表明，对于相干态，散射与声子振幅成正比。所观察到的声子的波矢延伸到激发波矢之外。纳米颗粒打破了晶格的离散平移对称性，使得能够产生大波矢相干声子。纳米颗粒对X射线光子的弹性散射为外差混频提供了参考，产生与声子振幅成正比的信号。
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