Zhang Guowei, Huang Shenyang, Wang Fanjie, Xing Qiaoxia, Song Chaoyu, Wang Chong, Lei Yuchen, Huang Mingyuan, Yan Hugen
Department of Physics, State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, 200433, Shanghai, China.
MIIT Key Laboratory of Flexible Electronics (KLoFE) and Xi'an Institute of Flexible Electronics, Northwestern Polytechnical University, 710072, Xi'an, Shaanxi, China.
Nat Commun. 2020 Apr 15;11(1):1847. doi: 10.1038/s41467-020-15699-7.
The strength of light-matter interaction is of central importance in photonics and optoelectronics. For many widely studied two-dimensional semiconductors, such as MoS, the optical absorption due to exciton resonances increases with thickness. However, here we will show, few-layer black phosphorus exhibits an opposite trend. We determine the optical conductivity of few-layer black phosphorus with thickness down to bilayer by infrared spectroscopy. On the contrary to our expectations, the frequency-integrated exciton absorption is found to be enhanced in thinner samples. Moreover, the continuum absorption near the band edge is almost a constant, independent of the thickness. We will show such scenario is related to the quanta of the universal optical conductivity of graphene (σ = e/4ħ), with a prefactor originating from the band anisotropy.
光与物质相互作用的强度在光子学和光电子学中至关重要。对于许多被广泛研究的二维半导体，如二硫化钼，由于激子共振引起的光吸收随厚度增加。然而，在这里我们将表明，少层黑磷呈现出相反的趋势。我们通过红外光谱法测定了厚度低至双层的少层黑磷的光电导率。与我们的预期相反，发现在较薄的样品中频率积分激子吸收增强。此外，带边附近的连续吸收几乎是恒定的，与厚度无关。我们将表明这种情况与石墨烯的通用光电导率量子（σ = e/4ħ）有关，其前置因子源于能带各向异性。
