Fig. 2: Orthogonal exceptional chain.
From: Symmetry-protected topological exceptional chains in non-Hermitian crystals
a Exceptional line (EL) confined in a symmetry-invariant plane by M-†or \({C}_{2}{{{{{{{\mathcal{T}}}}}}}}\) symmetry, separating the exact (light red) and broken (red) phases. b Orthogonal exceptional chain protected by two symmetries belonging to M-†or \({C}_{2}{{{{{{{\mathcal{T}}}}}}}}\), where ELs, confined in two perpendicular planes Π1 and Π2 connect at the chain point K0. In each plane, the lighter (darker) region denotes the exact (broken) phase.
