非线性电子-声子相互作用下声子重整化的第一性原理理论
First-principles theory of phonon renormalization from nonlinear electron-phonon interactions
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中文总结 AI 辅助
本文通过图解自能方法，首次从第一性原理研究非线性单电子-双声子相互作用对声子重整化的影响，发现其在整个布里渊区产生温度依赖的重整化，并在KTaO3中效应显著，为实验探测提供了特征信号。
中文摘要 AI 辅助
电子-声子相互作用会重整化声子频率和寿命，是固体动力学性质的核心。虽然这些效应通常在线性电子-声子耦合框架内描述，但非线性电子-声子相互作用对声子性质的作用在很大程度上仍未得到探索。在本工作中，我们在图解框架内研究了由长程线性单电子-单声子相互作用和非线性单电子-双声子相互作用引起的声子重整化。我们推导了相应的自能图，它们依赖于化学势和温度，并对两种极性半导体LiF和KTaO$_3$进行了第一性原理评估。在这两种材料中，这两个相互作用通道以定性不同的方式重整化声子谱。线性贡献尖锐地局域在布里渊区中心附近，而非线性过程将入射声子与整个谱中的其他支耦合起来。因此，它重整化了整个布里渊区的声子，其显著的温度依赖性由这些支的热占据所支配。这种行为为单电子-双声子耦合提供了清晰的实验特征。虽然LiF中的非线性声子重整化很小，但在KTaO$_3$中稍大，我们将其归因于室温下热占据声子支数量更多。我们的结果建立了一个通用框架，用于评估具有更强晶格涨落的材料（包括铅卤钙钛矿等软半导体）中非线性电子-声子效应对声子性质的影响。
英文摘要
Electron-phonon interactions renormalize phonon frequencies and lifetimes and are central to the dynamical properties of solids. While these effects are usually described within linear electron-phonon coupling, the role of nonlinear electron-phonon interactions for phonon properties remains largely unexplored. In this work, we study phonon renormalization arising from the long-range linear one-electron-one-phonon and the nonlinear one-electron-two-phonon interactions within a diagrammatic framework. We derive the corresponding self-energy diagrams, which depend on the chemical potential and temperature, and evaluate them from first principles for the two polar semiconductors LiF and KTaO$_3$. In both materials, the two interaction channels renormalize the phonon spectrum in qualitatively distinct ways. The linear contribution is sharply localized near the Brillouin-zone center, whereas the nonlinear process couples an incoming phonon to other branches throughout the spectrum. As a result, it renormalizes phonons across the entire Brillouin-zone, with a pronounced temperature dependence governed by the thermal occupation of those branches. This behavior provides a clean experimental signature of the one-electron-two-phonon coupling. While the nonlinear phonon renormalization is small in LiF, it is somewhat larger in KTaO$_3$, which we attribute to its greater number of thermally populated phonon branches at room temperature. Our results establish a general framework to assess nonlinear electron-phonon effects on the phonon properties in materials with stronger lattice fluctuations, including soft semiconductors such as lead-halide perovskites.
发表机构
- Institute of Science and Technology Austria (ISTA)（奥地利科学技术研究所）
- Theory of Quantum Systems and Complex Systems, Universiteit Antwerpen（安特卫普大学量子系统与复杂系统理论）
- Faculty of Physics, Computational Materials Physics, University of Vienna（维也纳大学物理学院计算材料物理系）
- Department of Physics and Astronomy “Augusto Righi”, Alma Mater Studiorum - Università di Bologna（博洛尼亚大学阿ugusto Righi物理与天文学系）
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