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arXiv · 1704.04713

Defect states emerging from a non-Hermitian flat band of photonic zero modes

Bingkun Qi·Lingxuan Zhang·Li Ge
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Abstract

We show the existence of a flat band consisting of photonic zero modes in a gain and loss modulated lattice system, as a result of the underlying non-Hermitian particle-hole symmetry. This general finding explains the previous observation in parity-time symmetric systems where non-Hermitian particle-hole symmetry is hidden. We further discuss the defect states in these systems, whose emergence can be viewed as an unconventional alignment of a pseudo-spin under the influence of a complex-valued pseudo-magnetic field. These defect states also behave as a chain with two types of links, one rigid in a unit cell and one soft between unit cells, as the defect states become increasingly localized with the gain and loss strength. A realistic photonic design is presented based on coupled InP/InGaAsP waveguides, and we also extend the discussion to two- and three-dimensional lattices.

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Bingkun Qi, Lingxuan Zhang, Li Ge. 2017-04-16. Defect states emerging from a non-Hermitian flat band of photonic zero modes. https://doi.org/10.1103/physrevlett.120.093901

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