Black phosphorus presents a very anisotropic crystal structure, making it a potential candidate for hyperbolic plasmonics, characterized by a permittivity tensor where one of the principal components is metallic and the other dielectric. Here we demonstrate that atomically thin black phosphorus can be engineered to be a hyperbolic material operating in a broad range of the electromagnetic spectrum from the entire visible spectrum to ultraviolet. With the introduction of an optical gain, a new hyperbolic region emerges in the infrared. The character of this hyperbolic plasmon depends on the interplay between gain and loss along the two crystalline directions.
@article{arxiv.1812.03062,
title = {Tuning 2D hyperbolic plasmons in black phosphorus},
author = {Edo van Veen and Andrei Nemilentsau and Anshuman Kumar and Rafael Roldán and Mikhail I. Katsnelson and Tony Low and Shengjun Yuan},
journal= {arXiv preprint arXiv:1812.03062},
year = {2019}
}