Interplay of Surface and Interior Modes in Exciton–Phonon Coupling at the Nanoscale,Nano Letters

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Interplay of Surface and Interior Modes in Exciton–Phonon Coupling at the Nanoscale
Nano Letters ( IF 9.6 ) Pub Date : 2021-10-05 , DOI: 10.1021/acs.nanolett.1c02953
Dipti Jasrasaria ₁ , Eran Rabani _{1,

2,

3}

Affiliation

Exciton–phonon coupling (EXPC) plays a key role in the optoelectronic properties of semiconductor nanocrystals (NCs), but a microscopic picture of EXPC is still lacking, particularly regarding the magnitude and scaling with NC size, the dependence on phonon frequency, and the role of the NC surface. The computational complexity associated with accurately describing excitons and phonons has limited previous theoretical studies of EXPC to small NCs, noninteracting electron–hole models, and/or a small number of phonon modes. Here, we develop an atomistic approach for describing EXPC in NCs of experimentally relevant sizes. We validate our approach by calculating the reorganization energies, a measure of EXPC, for CdSe and CdSe-CdS core–shell NCs, finding good agreement with experimental measurements. We demonstrate that exciton formation distorts the NC lattice primarily along the coordinates of low-frequency acoustic modes. Modes at the NC surface play a significant role in smaller NCs while interior modes dominate for larger systems.

中文翻译：

纳米级激子-声子耦合中表面和内部模式的相互作用

激子 - 声子耦合（EXPC）在半导体纳米晶体（NCs）的光电特性中起着关键作用，但仍然缺乏EXPC的微观图像，特别是关于NC尺寸的大小和比例，对声子频率的依赖性以及NC 曲面的作用。与准确描述激子和声子相关的计算复杂性已将以前的 EXPC 理论研究限制在小型 NC、非相互作用电子空穴模型和/或少量声子模式。在这里，我们开发了一种原子方法来描述实验相关大小的 NC 中的 EXPC。我们通过计算 CdSe 和 CdSe-CdS 核 - 壳 NC 的重组能（EXPC 的量度）来验证我们的方法，发现与实验测量结果非常吻合。我们证明激子的形成主要沿着低频声学模式的坐标扭曲了 NC 晶格。NC 表面的模式在较小的 NC 中起着重要作用，而内部模式在较大的系统中占主导地位。

更新日期：2021-10-27

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