Despite being only a few atoms thick, single-layer two-dimensional (2D) materials display strong electron–photon interactions that could be utilized in efficient light modulators on extreme subwavelength scales. In various applications involving light modulation and manipulation, materials with strong optical response at different wavelengths are required. Using qualitative analytical modeling and first-principles calculations, we determine the theoretical limit of the maximum optical response such as absorbance (A) and reflectance (R) in 2D materials and also conduct a computational survey to seek out those with best A and R in various frequency ranges, from mid-infrared to deep-ultraviolet. We find that 2D boron has broadband reflectance R > 99% for >100 layers, surpassing conventional thin films of bulk metals such as silver. Moreover, we identify 2D monolayer semiconductors with maximum response, for which we obtain quantitative estimates by calculating quasiparticle energies and accounting for excitonic effects by solving the Bethe–Salpeter equation. We found several monolayer semiconductors with absorbances ≳30% in different optical ranges, which are more than half of the maximum possible value, A_lim = 1/2, for a freestanding 2D material. Our study predicts 2D materials which can potentially be used in ultrathin reflectors and absorbers for optoelectronic application in various frequency ranges.

中文翻译：

---

追求2D材料以实现最大光学响应

尽管只有几个原子厚，但是单层二维（2D）材料仍显示出强大的电子-光子相互作用，可以在极端的亚波长范围内将其用于有效的光调制器中。在涉及光调制和操纵的各种应用中，需要在不同波长下具有强光学响应的​​材料。使用定性分析模型和第一性原理计算，我们确定了2D材料中最大光学响应（例如吸收率（A）和反射率（R））的理论极限，并进行了计算调查以找出具有最佳A和R的那些在从中红外到深紫外的各种频率范围内。我们发现2D硼对于> 100层的宽带反射率R > 99％，超过了诸如银之类的块状金属的常规薄膜。此外，我们确定了具有最大响应的二维单层半导体，为此，我们可以通过计算准粒子能量并通过解决Bethe–Salpeter方程来考虑激子效应来获得定量估计。我们发现了几种单层半导体，它们在不同的光学范围内的吸光度为≳30％，是最大可能值A _lim的一半以上。= 1/2，对于独立的2D材料。我们的研究预测，二维材料可以在各种频率范围内用于光电应用的超薄反射器和吸收器。