Signatures of Dimensionality and Symmetry in Exciton Band Structure: Consequences for Exciton Dynamics and Transport,Nano Letters

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Signatures of Dimensionality and Symmetry in Exciton Band Structure: Consequences for Exciton Dynamics and Transport
Nano Letters ( IF 9.6 ) Pub Date : 2021-08-31 , DOI: 10.1021/acs.nanolett.1c02352
Diana Y Qiu ₁ , Galit Cohen ₂ , Dana Novichkova ₂ , Sivan Refaely-Abramson ₂

Affiliation

Exciton dynamics, lifetimes, and scattering are directly related to the exciton dispersion or band structure. Here, we present a general theory for exciton band structure within both ab initio and model Hamiltonian approaches. We show that contrary to common assumption, the exciton band structure contains nonanalytical discontinuities—a feature which is impossible to obtain from the electronic band structure alone. These discontinuities are purely quantum phenomena, arising from the exchange scattering of electron–hole pairs. We show that the degree of these discontinuities depends on materials’ symmetry and dimensionality, with jump discontinuities occurring in 3D and different orders of removable discontinuities in 2D and 1D, whose details depend on the exciton degeneracy and material thickness. We connect these features to the early stages of exciton dynamics, radiative lifetimes, and diffusion constants, in good correspondence with recent experimental observations, revealing that the discontinuities in the band structure lead to ultrafast ballistic transport and suggesting that measured exciton diffusion and dynamics are influenced by the underlying exciton dispersion.

中文翻译：

激子带结构中的维度和对称性特征：激子动力学和传输的后果

激子动力学、寿命和散射与激子色散或能带结构直接相关。在这里，我们提出了从头算内激子能带结构的一般理论和模型哈密顿方法。我们表明，与通常的假设相反，激子能带结构包含非分析不连续性——这是仅从电子能带结构中无法获得的特征。这些不连续性是纯粹的量子现象，由电子-空穴对的交换散射引起。我们表明，这些不连续性的程度取决于材料的对称性和维度，跳跃不连续性发生在 3D 和 2D 和 1D 中不同阶的可移除不连续性，其细节取决于激子简并性和材料厚度。我们将这些特征与激子动力学、辐射寿命和扩散常数的早期阶段联系起来，与最近的实验观察结果非常吻合，

更新日期：2021-09-22

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