Interlayer Excitons with Large Optical Amplitudes in Layered van der Waals Materials,Nano Letters

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Interlayer Excitons with Large Optical Amplitudes in Layered van der Waals Materials
Nano Letters ( IF 9.6 ) Pub Date : 2018-04-17 00:00:00 , DOI: 10.1021/acs.nanolett.8b00438
Thorsten Deilmann ₁ , Kristian Sommer Thygesen _{1,

2}

Affiliation

Vertically stacked two-dimensional materials form an ideal platform for controlling and exploiting light–matter interactions at the nanoscale. As a unique feature, these materials host electronic excitations of both intra- and interlayer type with distinctly different properties. In this Letter, using first-principles many-body calculations, we provide a detailed picture of the most prominent excitons in bilayer MoS₂, a prototypical van der Waals material. By applying an electric field perpendicular to the bilayer, we explore the evolution of the excitonic states as the band alignment is varied from perfect line-up to staggered (Type II) alignment. For moderate field strengths, the lowest exciton has intralayer character and is almost independent of the electric field. However, we find higher lying excitons that have interlayer character. They can be described as linear combinations of the intralayer B exciton and optically dark charge transfer excitons, and interestingly, these mixed interlayer excitons have strong optical amplitude and can be easily tuned by the electric field. The first-principles results can be accurately reproduced by a simple excitonic model Hamiltonian that can be straightforwardly generalized to more complex van der Waals materials.

中文翻译：

层状范德华材料中具有大光学幅度的层间激子

垂直堆叠的二维材料形成了一个理想的平台，可以控制和利用纳米级的光-物质相互作用。作为一种独特的功能，这些材料可以同时具有层间和层间类型的电子激发，并且具有明显不同的特性。在这封信中，使用第一性原理多体计算，我们提供了双层MoS _2中最突出的激子的详细图片，范德华原型材料。通过施加垂直于双层的电场，当带的排列从完美排列到交错排列（II型）变化时，我们探索了激子态的演化。对于中等的场强，最低的激子具有层内特性，并且几乎与电场无关。然而，我们发现具有层间特征的较高级激子。可以将它们描述为层内B激子和光学上暗电荷转移激子的线性组合，有趣的是，这些混合的层间激子具有很强的光学振幅，可以很容易地通过电场进行调谐。第一原理的结果可以通过简单的激子模型哈密顿量精确地再现，该模型可以直接推广到更复杂的范德华材料。

更新日期：2018-04-17

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