The optical conductivity of few-layer black phosphorus by infrared spectroscopy.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32296052.
- Also identified by DOI 10.1038/s41467-020-15699-7 and PMC identifier 7160205.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The strength of light-matter interaction is of central importance in photonics and optoelectronics. For many widely studied two-dimensional semiconductors, such as MoS<sub>2</sub>, 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<sub>0</sub> = e<sup>2</sup>/4ħ), with a prefactor originating from the band anisotropy.