从第一性原理探究有限波数下固体中等容加热电子的激发特征
Excitation signatures of isochorically heated electrons in solids at finite wavenumber explored from first principles
AI总结：
本文用第一性原理线性响应含时密度泛函理论模拟XFEL加热的Al和Si，揭示有限波数下等离激元红移、双峰及低频峰—谷结构等可由XRTS验证的新特征。
摘要：
利用现代X射线自由电子激光（XFEL）对固体进行超快加热，会产生一组独特条件，其特征是受热电子与冷离子晶格同时存在。在本工作中，我们采用第一性原理线性响应含时密度泛函理论模拟，分析了电子加热对具有面心立方晶格的体相铝（Al）以及具有金刚石晶体结构的硅（Si）中动态结构因子（DSF）的影响。我们发现，在这两种材料中，集体等离激元激发均出现热诱导红移。此外，我们表明，由于Landau阻尼区域向更小的波数扩展，Al中电子的加热可导致双等离激元峰的形成。最后，我们证明，热效应会在小频率下Si的DSF中产生可测量且独特的特征（峰—谷结构）。我们的模拟表明，在X射线驱动固体的谱中，尤其在有限动量转移处，存在多种新特征，这些特征可在即将于各XFEL装置开展的X射线Thomson散射（XRTS）实验中进行探测。
英文摘要：
Ultrafast heating of solids with modern X-ray free electron lasers (XFELs) leads to a unique set of conditions that is characterized by the simultaneous presence of heated electrons in a cold ionic lattice. In this work, we analyze the effect of electronic heating on the dynamic structure factor (DSF) in bulk Aluminium (Al) with a face-centered cubic lattice and in silicon (Si) with a crystal diamond structure using first-principles linear-response time-dependent density functional theory simulations. We find a thermally induced red shift of the collective plasmon excitation in both materials. In addition, we show that the heating of the electrons in Al can lead to the formation of a double-plasmon peak due to the extension of the Landau damping region to smaller wavenumbers. Finally, we demonstrate that thermal effects generate a measurable and distinct signature (peak-valley structure) in the DSF of Si at small frequencies. Our simulations indicate that there is a variety of new features in the spectrum of X-ray-driven solids, specifically at finite momentum transfer, which can probed in upcoming X-ray Thomson scattering (XRTS) experiments at various XFEL facilities.
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