Phonon-Induced Localization of Excitons in Molecular Crystals from First Principles
Phonon-Induced Localization of Excitons in Molecular Crystals from First Principles
复制标题
DOI：
10.1103/physrevlett.130.086401
复制
发表时间：
2023-02-24
影响因子：
8.6
通讯作者：
Neaton, Jeffrey B.
中科院分区：
文献类型：
--
作者：
Alvertis, Antonios M.;Haber, Jonah B.;Neaton, Jeffrey B.
分子系统中激子的空间范围支撑着它们的光物理学和光电应用的实用性。据报道，声子会导致激子局域化和离域化。然而，缺乏对声子引起的（去）局域化的微观理解，特别是局域态如何形成、特定振动的作用以及量子和热核涨落的相对重要性。在这里，我们使用密度泛函理论、从头算 GW-Bethe-Salpeter 方程方法、有限差分和路径积分技术，对固体并五苯（一种典型的分子晶体）中的这些现象进行了第一性原理研究，捕获了束缚激子的形成、所有级数的激子-声子耦合以及声子非谐性。我们发现，对于并五苯，零点核运动会导致均匀的强局域化，而热运动仅对类 Wannier-Mott 激子提供额外的局域化。非简谐效应驱动温度依赖性局域化，虽然这种效应阻止了高度离域激子的出现，但我们探索了实现这些效应的条件。
The spatial extent of excitons in molecular systems underpins their photophysics and utility for optoelectronic applications. Phonons are reported to lead to both exciton localization and delocalization. However, a microscopic understanding of phonon-induced (de)localization is lacking, in particular, how localized states form, the role of specific vibrations, and the relative importance of quantum and thermal nuclear fluctuations. Here, we present a first-principles study of these phenomena in solid pentacene, a prototypical molecular crystal, capturing the formation of bound excitons, exciton-phonon coupling to all orders, and phonon anharmonicity, using density functional theory, the ab initio GW-Bethe-Salpeter equation approach, finite-difference, and path integral techniques. We find that for pentacene zero-point nuclear motion causes uniformly strong localization, with thermal motion providing additional localization only for Wannier-Mott-like excitons. Anharmonic effects drive temperature-dependent localization, and, while such effects prevent the emergence of highly delocalized excitons, we explore the conditions under which these might be realized.