揭示电子-声子散射在固体高次谐波退相中的作用
Unveiling the Role of Electron-Phonon Scattering in Dephasing High-Order Harmonics in Solids
AI总结：
该研究结合单原子层与体相半导体的波长依赖实验及从头算模拟，提出动量依赖退相时间，证明电子-声子散射是固体HHG退相的主导机制。
摘要：
固体中的高次谐波产生（HHG）深受外部激光场驱动的相干电子-空穴运动退相的影响。这种退相背后的确切物理机制对于准确理解和建模HHG光谱至关重要，但一直难以明确且存在争议，通常更多被视为经验观察，而非牢固确立的原理。在本工作中，我们呈现了关于单原子层和体相半导体中HHG波长依赖性的综合实验结果。这些结果进一步得到严格数值模拟的佐证，模拟采用了从头算实时、实空间含时密度泛函理论和半导体Bloch方程。我们的实验观察要求引入一个新概念：HHG中依赖动量的退相时间。通过详细分析，我们确定依赖动量的电子-声子散射是驱动退相的主要机制。这一认识显著推进了对固体中退相现象的理解，解决了该领域长期存在的争论。此外，我们的发现为一种测定电子-声子散射率的新型全光学测量技术铺平了道路，并确立了凝聚态物质中HHG效率的基本极限。
英文摘要：
High-order harmonic generation (HHG) in solids is profoundly influenced by the dephasing of the coherent electron-hole motion driven by an external laser field. The exact physical mechanisms underlying this dephasing, crucial for accurately understanding and modelling HHG spectra, have remained elusive and controversial, often regarded more as an empirical observation than a firmly established principle. In this work, we present comprehensive experimental findings on the wavelength-dependency of HHG in both single-atomic-layer and bulk semiconductors. These findings are further corroborated by rigorous numerical simulations, employing ab initio real-time, real-space time-dependent density functional theory and semiconductor Bloch equations. Our experimental observations necessitate the introduction of a novel concept: a momentum-dependent dephasing time in HHG. Through detailed analysis, we pinpoint momentum-dependent electron-phonon scattering as the predominant mechanism driving dephasing. This insight significantly advances the understanding of dephasing phenomena in solids, addressing a long-standing debate in the field. Furthermore, our findings pave the way for a novel, all-optical measurement technique to determine electron-phonon scattering rates and establish fundamental limits to the efficiency of HHG in condensed matter.
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