Non-Hermitian topological phase transitions in superlattices and the optical Dirac equation

Optical superlattices with sublattice symmetry subjected to a synthetic imaginary gauge field undergo a topological phase transition in theBloch energy spectrum, characterized by the change of a spectral winding number. For a narrow gap, the phase transition is of universal form and described by a non-HermitianDirac equation with Lorentz-symmetry violation. A simple photonic system displaying such a phase transition is discussed, which is based on light coupling in co-propagating gratings. (C) 2021 Optical Society of America

Automated summary

This study discusses the topological phase transition of optical superlattices with sublattice symmetry under a synthetic imaginary gauge field, described by the change of a spectral winding number. The phase transition for a narrow gap is of universal form and can be described by a non-Hermitian Dirac equation.