Twisted bilayers of transition metal dichalcogenides (TMDs) have revealed a rich exciton landscape including hybrid excitons and spatially trapped moiré excitons that dominate the optical response of the material. Recent studies have shown that in the low-twist-angle regime, the lattice undergoes a significant relaxation in order to minimize local stacking energies. Here, large domains of low energy stacking configurations emerge, deforming the crystal lattices via strain and consequently impacting the electronic band structure. However, so far the direct impact of atomic reconstruction on the exciton energy landscape and the optical properties has not been well understood. Here, we apply a microscopic and material-specific approach and predict a significant change in the potential depth for moiré excitons in a reconstructed lattice, with the most drastic change occurring in naturally stacked TMD homobilayers. We show the appearance of multiple flat bands and a significant change in the position of trapping sites compared to the rigid lattice. Most importantly, we predict a multipeak structure emerging in optical absorption of ${\mathrm{WSe}}_2$ homobilayers—in contrast to the single peak that dominates the rigid lattice. This finding can be exploited as an unambiguous signature of atomic reconstruction in optical spectra of moiré excitons in naturally stacked twisted homobilayers.

中文翻译：

---

原子重构对扭曲 TMD 同双层光谱的影响

过渡金属二硫化物（TMD）的扭曲双层揭示了丰富的激子景观，包括混合激子和空间捕获的莫尔激子，它们主导了材料的光学响应。最近的研究表明，在低扭转角状态下，晶格会经历显着的弛豫，以最大限度地减少局部堆积能。在这里，出现了低能量堆叠结构的大域，通过应变使晶格变形，从而影响电子能带结构。然而，到目前为止，原子重构对激子能量景观和光学性质的直接影响尚未得到很好的理解。在这里，我们应用微观和材料特定的方法，预测重构晶格中莫尔激子的潜在深度的显着变化，其中最剧烈的变化发生在自然堆叠的 TMD 同双层中。我们展示了多个平带的出现以及与刚性晶格相比捕获位点位置的显着变化。最重要的是，我们预测在光吸收中会出现多峰结构${\mathrm{硒化钨}}_2$同双层——与主导刚性晶格的单峰相反。这一发现可以用作自然堆叠的扭曲同双层中莫尔激子光谱中原子重构的明确特征。