Switchable anapole states in Sb₂Se₃-based phase-change nanoresonators

Phase-change nanophotonic platforms offer a promising route toward tunable and reconfigurable optical functionalities at the nanoscale. Active and non-volatile control over radiative and non-radiative modes at the nanoscale represents a crucial goal for integrated photonics. In this work, we demonstrate that Sb₂Se₃ can support multiple Mie resonance modes, including electric dipole (ED) and anapole states. Then, we propose and demonstrate that the phase-change characteristics of Sb₂Se₃ enable reversible switching between an electric dipole mode and a toroidal-dipole-dominated anapole state in a single nanoresonator. This switching stems from the abrupt refractive-index change induced by the phase transition, which not only redshifts the resonance but, more importantly, precisely modulates the interference conditions among multipoles. Our study provides a fundamentally distinct, high-contrast building block for non-volatile, programmable metasurfaces and dynamic nanophotonic devices.