Cooperative effects allow for fascinating characteristics in light–matter interacting systems. Here, we study naturally occurring superradiant coupling in a class of quasi–two-dimensional, layered semiconductor systems. We perform optical absorption experiments of the lowest exciton for transition-metal dichalcogenides with different numbers of atomic layers. We examine two representative materials, ${\mathrm{MoSe}}_2$ and ${\mathrm{WSe}}_2$, using incoherent broadband white light. The measured transmission at the A exciton resonance does not saturate for optically thick samples consisting of hundreds of atomic layers, and the transmission varies nonmonotonously with the layer number. A self-consistent microscopic calculation reproduces the experimental observations, clearly identifying superradiant coupling effects as the origin of this unexpected behavior.

中文翻译：

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过渡金属二卤化物中的超辐射耦合效应

合作效应使光物质相互作用系统具有令人着迷的特性。在这里，我们研究了一类准二维分层半导体系统中自然发生的超辐射耦合。我们对具有不同原子层数的过渡金属二卤化物进行了最低激子的光吸收实验。我们研究了两种代表性的材料，${\mathrm{硒化钼}}_{\mathrm{2个}}$ 和 ${\mathrm{硒化钨}}_{\mathrm{2个}}$，使用不相干的宽带白光。对于由数百个原子层组成的光学厚度样品，在A激子共振下测得的透射率不会饱和，并且透射率随层数非单调变化。自洽的微观计算重现了实验观察结果，清楚地确定了超辐射耦合效应是这种意外行为的根源。