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Effective theory of quadratic degeneracies
We present an effective theory for the Bloch functions of a two-dimensional square lattice near a quadratic degeneracy point. The degeneracy is protected by the symmetries of the crystal, and breaking these symmetries can ...
Reflection-free one-way edge modes in a gyromagnetic photonic crystal
We point out that electromagnetic one-way edge modes analogous to quantum Hall edge states, originally predicted by Raghu and Haldane in 2D photonic crystals possessing Dirac point-derived band gaps, can appear in more ...
Dark-state polaritons in single- and double-Λ media
We derive the properties of polaritons in single-Λ and double-Λ media using a microscopic equation-of-motion technique. In each case, the polaritonic dispersion relation and composition arise from a matrix eigenvalue ...