Exceptional points in the scattering resonances of a sphere dimer
Phys. Rev. A 113, 063520 – Published 15 June, 2026
DOI: https://doi.org/10.1103/b7qp-shcg
Abstract
We investigate exceptional points of degeneracy (EPDs) in electromagnetic scattering of a sphere dimer from the electroquasistatic limit to the fully retarded regime. In the quasistatic limit, we prove that -symmetric configurations, realized by spheres with complex-conjugate susceptibilities, host EPDs. Beyond this limit, retardation breaks symmetry; nevertheless, by jointly tuning the material dispersions of the two spheres, we derive analytic synthesis conditions for realizing EPDs at real frequencies. Near an EPD, we show that single-parameter perturbations yield the characteristic square-root splitting of the eigenfrequencies, and we quantify its impact on scattering, extinction, and absorption, clarifying sensing implications.
