Non-Hermitian ideal Weyl photonic metamaterials and polarization-momentum resolved ultrahigh absorption.

In the past decade, there has been a significant surge of interest in investigating non-Hermitian Hamiltonians, particularly in photonics. The eigenvalues of general non-Hermitian Hamiltonians are complex and possess unique topological features such as exceptional degeneracy. The introduction of non-Hermitian perturbations into Weyl semimetals can transform Weyl points into exceptional rings characterized by multiple topological invariants. However, the ideal realization of Weyl rings within practical three-dimensional structures has remained a significant challenge. In this work, we extend artificial photonic metamaterial structures that can transform ideal Weyl points into non-Hermitian exceptional rings. We show the associated intriguing polarization-momentum ultrahigh absorption, which enables what we believe to be a new device application in non-Hermitian photonics. Our study not only proposes the practical model for ideal non-Hermitian photonic Weyl exceptional rings but also opens the gate of non-Hermitian scattering characterization.