Revisiting the local-density-of-states enhancement at exceptional points
Phys. Rev. A 113, 053524 – Published 18 May, 2026
DOI: https://doi.org/10.1103/h8n4-lw4b
Abstract
Spectral engineering has enabled the design of electromagnetic structures with enhanced local density of states (LDOS), a key ingredient for wave-mediated technologies. Recent studies motivated by parity-time ()-symmetric systems with reactive coupling have suggested that exceptional point (EP) degeneracy may provide a universal route to LDOS enhancement. In this study, we demonstrate that the presence of an EP alone does not guarantee LDOS enhancement. Instead, we rigorously show that EP-induced LDOS enhancement is critically governed by the phase correlation between the coalescing eigenvectors, as revealed by a Green's function formalism combined with Jordan chain analysis. As a result, the maximum LDOS can emerge away from the EP, even in passive systems, in sharp contrast to reactively coupled configurations where the EP coincides with maximal enhancement. Full wave simulations of coupled meta-atoms serve as a representative example that confirms the theoretical predictions and demonstrates experimentally accessible implementations.
