Opportunities in phosphorene plasmonic metasurfaces

We investigate the use of black phosphorus thin films in infrared plasmonics and discuss spatial dispersion effects. For appropriate film thickness, black phosphorus exhibits a moderate bandgap suitable for operation in this frequency band, and the intrinsic anisotropy of its conductivity tensor provides exciting possibilities in metasurfaces/reflectarray design, such as polarization-dependent devices and unusual topological transitions for plasmons induced by electrical or mechanical bias. We study the limits on plasmon confinement and field enhancement imposed by spatial dispersion and demonstrate that these bounds are looser than in graphene. These findings may lead to infrared plasmonic devices enabling light-matter interactions beyond the capabilities of other plasmonic materials, with exciting applications in sensing, thermal imaging, and heat scavenging.