Localized surface plasmons in a Weyl semimetal nanosphere

In this study, we investigate the localized surface-plasmon modes of a subwavelength spherical nanoparticle composed of a Weyl semimetal, taking into account the axion modification of electrodynamics. We derive analytical solutions for dipole and quadrupole normal modes by employing the quasistatic approximation. The axion term leads to modified Fr"ohlich conditions, resulting in multiple nondegenerate plasmonic resonances with distinct polarization dependencies. In contrast with isotropic conventional metals, the magnetoelectric properties of Weyl semimetals enable an incident electromagnetic field, with the electric field transverse to the surface of the sphere, to excite a localized surface plasmon.