Dynamical Quantum Properties of Phonons in Crystals

晶体中声子的动态量子特性

• 批准号: 417259631
• 负责人: Privatdozent Dr. Michael Wörner
• 金额: --
• 依托单位: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/417259631?language=en
• 关键词: Dynamical; Quantum; Properties; Phonons; Crystals

The present proposal aims at a combined experimental and theoretical study of the dynamical quantum properties of phonons in crystals. The joint experimental activities in Berlin (Michael Woerner) and theoretical calculations in Luxembourg (Alexandre Tkatchenko) aim at understanding fundamental microscopic mechanisms which underlie ultrafast atomic motions and electronic charge redistribution processes in crystalline matter for which quantum properties of phonons play a significant role. Experiments and theory will focus on coherent time-dependent processes of phonons. One part of the planned activities focuses on the coherent manipulation and fully phase-resolved detection of the density matrix of multi-phonon modes in crystals using a combination of coherent n-th-order Raman excitations and coherent THz emission which allows for exciting and probing "non-classical" states in the density matrix of multi-phonon modes. Another scientific goal of this proposal is the detailed spatio-temporal characterization (with atomic length and time resolution) of the soft mode phonons in ferroelectrics and molecular crystals. In contrast to "conventional" optical phonons in crystals soft modes have a pronounced hybrid character of nuclear motions and electronic charge relocations. Multi-dimensional terahertz spectroscopy and femtosecond x-ray diffraction are the main experimental techniques of the project. Since the electronic contribution to soft-mode currents is by orders of magnitudes larger than that of the nuclei, the Born Oppenheimer approximation in a theoretical description of soft modes is no longer a good approximation because the expectation value of the kinetic energy of the nuclei contains significant inter-electronic potential surface terms. The theoretical part of this proposal which starts with a well-established background based on van der Waals inclusive density functional theory (DFT) will be explored and extended into a direction to study theoretically such "non-Born-Oppenheimer" effects of phonons crystals.

本提案的目的是对晶体中声子的动力量子特性的合并实验和理论研究。卢森堡（Alexandre tkatchenko）中柏林（迈克尔·沃恩（Michael Woerner））的联合实验活动和理论计算旨在理解基本的显微镜机制，这些微观机制是超级原子动作和电子电荷重新分布过程中晶体特性中发挥重要作用的量子性质的重新分布过程的基础。实验和理论将集中于声子的一致时间依赖性过程。计划中的活动的一部分侧重于使用连贯的n-th阶拉曼激发和相干Thz发射的相干n-th阶拉曼激发和相干发射的组合，对晶体中多光谱模式的密度矩阵进行了完全分辨的检测，从而使“多个phonon模式的密度矩阵中的非经典”状态。该建议的另一个科学目标是铁电和分子晶体中软模式声子的详细时空表征（具有原子长度和时间分辨率）。与晶体中的“常规”光音子相比，软模式具有明显的核运动和电子电荷重新定位的混合特征。多维的Terahertz光谱和飞秒X射线衍射是该项目的主要实验技术。由于对软模式电流的电子贡献是通过大小的大小的顺序，因此在软模式的理论描述中，天生的Oppenheimer近似不再是一个良好的近似值，因为核的预期值包含了重要的优势间互电势表面项。该提案的理论部分是从基于范德华包含密度功能理论（DFT）的良好背景开始的，并将探索，并扩展到理论上研究这种“非出生的 - 邻苯二海”效应的方向。