Bismuth chalcogenides have emerged as an intriguing option in nanophotonics due to their unique properties, including a significant dielectric function and topologically protected surface states in the terahertz (THz) range. Our study focuses on the optical response of Bi2Se3 topological-insulator nanospheres, where topological properties arise, influencing electromagnetic modes and field enhancement. Within a fully electrodynamic picture, we explore the emergence of unreported magnetic modes induced by Dirac plasmon polaritons resulting from terahertz photon and Dirac electron interactions. We observe their profound impact on electric and magnetic transitions of quantum emitters near Bi2Se3 nanospheres, resulting in record - high Purcell factors. Our research highlights the rich optical response of Bi2Se3 nanospheres, involving contributions from both phonon polaritons and topologically protected surface states. Our findings confirm the emergence of topological optical modes in Bi2Se3 spherical TIs, positioning them as promising candidates for advancements in strong light-matter interactions in topological nanophotonics and THz technologies.
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