动态衍射理论用于通过暗场X射线显微镜成像时间依赖的扩散散射相干声子
Dynamical diffraction formalism for imaging time-dependent diffuse scattering from coherent phonons with Dark-Field X-ray Microscopy
AI总结：
本文提出利用暗场X射线显微镜通过时间依赖的强度振荡侧带研究相干声子动力学，克服了传统方法的频率分辨率限制，实现了空间和倒易空间的联合分析。
摘要：
相干声子的阻尼决定了声学谐振器的质量因子上限，在先进电信和量子信息技术中起关键作用。然而，使用传统表面技术探测其GHz范围内的衰变仍具挑战性。暗场X射线显微镜（DFXM）通过高空间和角分辨率实现了对bulk材料中应变场和位错的穿透式、非破坏性、全场成像。我们先前基于布拉格峰位移描述DFXM信号，允许通过样品深度重建相干声子的频率谱。然而，通过跟踪布拉格峰位移研究声子动力学的方法限制了最高声子频率的研究上限，由测量的空间分辨率决定。本文讨论如何利用DFXM通过时间依赖的强度振荡侧带研究相干声子动力学，同时允许在实空间和倒易空间中研究相干声子动力学，克服了由布拉格峰跟踪的实空间分辨率所施加的频率分辨率限制。使用Takagi-Taupin动态衍射理论，我们建立了研究相干声子动力学的空间和倒易空间分辨率，并评估了观测长寿命强度振荡的条件。最后，我们提出实验策略以优化激发带宽和倒易空间选择性。本文中的理论框架使设计DFXM实验成为可能，用于对bulk晶体材料中声子衰减和声子-缺陷相互作用进行定量、频率分辨的测量。
英文摘要：
Coherent acoustic phonons, whose damping sets the upper bound of quality factors in acoustic resonators, play a critical role in advanced telecommunication and quantum information technologies. Yet, probing their decay in the GHz regime remains challenging using conventional surface-based techniques. Dark-field X-ray microscopy (DFXM) offers a solution by enabling through-depth, non-destructive and full-field imaging of strain fields and dislocations inside bulk materials with high spatial and angular resolution. We previously used kinematic diffraction theory to describe DFXM signals based on how the Bragg peak shifts due to the strain wave, allowing us to reconstruct the frequency spectrum of coherent phonons as a function of depth through the sample. The approach of tracking the Bragg peak shifts to study phonon dynamics, however, places an upper-bound to the highest phonon frequency that can be studied, determined by the spatial resolution of the measurement. In this work, we discuss how coherent phonon dynamics can be studied with DFXM from time-dependent intensity oscillation sidebands. This approach simultaneously allows studying coherent phonon dynamics in real and reciprocal space, overcoming frequency resolution limits imposed by the real-space resolution of Bragg-peak tracking. Using Takagi-Taupin dynamical diffraction formalism, we establish the spatial and reciprocal space resolution achievable for studying the coherent phonon dynamics and evaluate conditions for observing long-lived intensity oscillations. We close by proposing experimental strategies to optimize excitation bandwidths and reciprocal-space selectivity. The formalism in the paper enables the design of DFXM experiments for quantitative, frequency-resolved measurements of acoustic phonon decay and phonon-defect interactions in bulk crystalline materials.
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