温度依赖的非线性光学第一性原理研究：少层MoS$_2$中的二次谐波产生
Temperature-Dependent nonlinear optics from first-principles: Second-Harmonic Generation in few-layers MoS$_2$
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中文总结 AI 辅助
提出第一性原理实时方法，通过准粒子重整化与退相干项引入有限温度效应，应用于少层MoS$_2$的二次谐波产生，揭示其非平凡温度依赖性及声子耦合机制。
中文摘要 AI 辅助
我们提出了一种第一性原理实时方法，用于研究固体在有限温度下的非线性响应。有限温度效应通过准粒子能量的重整化以及一个与准粒子寿命成正比的退相干项来包含。我们利用密度泛函微扰理论计算晶格动力学的电子-声子矩阵元，然后从电子自能的Fan项和Debye-Waller项计算准粒子重整化和寿命。电子激发在独立粒子近似水平上处理。我们将该方法应用于单层和三层MoS$_2$的二次谐波产生（SHG）。我们观察到SHG具有非平凡的温度依赖性，这是由于强烈的晶体动量依赖的准粒子重整化所致。通过声子模式分析，我们发现与声学模和剪切模的耦合分别决定了单层和三层MoS$_2$中整体的晶体动量依赖性。SHG的非平凡温度依赖性有助于解释在给定激光能量下，单层MoS$_2$中观察到的SHG强度随温度升高而增加的现象[Adv. Optical Mater. 8, 2000441 (2020)]。
英文摘要
We present a first-principles real-time approach to study non-linear response of solids at finite temperature. Finite temperature effects are included as renormalization of the quasiparticle energies and a dephasing term proportional to the quasiparticle lifetimes. We evaluate electron-phonon matrix elements from Density-Functional Perturbation Theory for lattice dynamics and then calculate quasiparticles renormalization and lifetime from the Fan and Debye-Waller terms of the electron self-energy. Electron excitations are treated at the independent particle level of approximation. We apply the approach to the second-harmonic generation (SHG) in monolayer and trilayer MoS$_2$. We observe a nontrivial temperature-dependence of the SHG due to a strong crystal-momentum dependent quasiparticle renormalization. From the phonon-mode analysis we find that the coupling with acoustic and shear modes determines the overall crystal-momentum dependence respectively in monolayer and trilayer MoS$_2$. The nontrivial temperature-dependence of the SHG can help rationalize the increase of SHG intensity with increasing temperature observed in monolayer MoS$_2$ at a given laser energy [Adv. Optical Mater. 8, 2000441 (2020)].
发表机构
- Queen’s University Belfast（贝尔法斯特女王大学）
- European Theoretical Spectroscopy Facilities (ETSF)（欧洲理论光谱设施）
- CNRS/Aix-Marseille Université, Centre Interdisciplinaire de Nanoscience de Marseille UMR 7325（法国国家科学研究中心/艾克斯-马赛大学，马赛跨学科纳米科学中心 UMR 7325）
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