Exceptional Points in the Scattering Resonances of a Sphere Dimer

Emanuele Corsaro; Filippo Capolino; Carlo Forestiere

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arXiv · 2512.24104

Exceptional Points in the Scattering Resonances of a Sphere Dimer

Emanuele Corsaro·Filippo Capolino·Carlo Forestiere

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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 $\parity\trev$-symmetric configurations, realized by spheres with complex-conjugate susceptibilities, host EPDs. Beyond this limit, retardation breaks $\mathscr{PT}$-symmetry; nevertheless, by jointly tuning the material dispersion of the two spheres, we derive analytic synthesis conditions for realizing EPDs at \textit{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.

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Emanuele Corsaro, Filippo Capolino, Carlo Forestiere. 2025-12-30. Exceptional Points in the Scattering Resonances of a Sphere Dimer. https://arxiv.org/abs/2512.24104

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