6,083 research outputs found
Effects of non-Hermitian perturbations on Weyl Hamiltonians with arbitrary topological charges
We provide a systematic study of non-Hermitian topologically charged systems.
Starting from a Hermitian Hamiltonian supporting Weyl points with arbitrary
topological charge, adding a non-Hermitian perturbation transforms the Weyl
points to one-dimensional exceptional contours. We analytical prove that the
topological charge is preserved on the exceptional contours. In contrast to
Hermitian systems, the addition of gain and loss allows for a new class of
topological phase transition: when two oppositely charged exceptional contours
touch, the topological charge can dissipate without opening a gap. These
effects can be demonstrated in realistic photonics and acoustics systems.Comment: 11 pages, 9 figure
Photonic Chern insulator through homogenization of an array of particles
We propose a route towards creating a metamaterial that behaves as a photonic
Chern insulator, through homogenization of an array of gyromagnetic cylinders.
We show that such an array can exhibit non-trivial topological effects,
including topologically non-trivial band gaps and one-way edge states, when it
can be homogenized to an effective medium model that has the Berry curvature
strongly peaked at the wavevector k=0. The non-trivial band topology depends
only on the parameters of the cylinders and the cylinders' density, and can be
realized in a wide variety of different lattices including periodic,
quasi-periodic and random lattices. Our system provides a platform to explore
the interplay between disorder and topology and also opens a route towards
synthesis of topological meta-materials based on the self-assembly approach.Comment: 15 pages, 4 figure
A Photonic Crystal Slab Laplace Differentiator
We introduce an implementation of a Laplace differentiator based on a
photonic crystal slab that operates at transmission mode. We show that the
Laplace differentiator can be implemented provided that the guided resonances
near the point exhibit an isotropic band structure. Such a device may
facilitate nanophotonics-based optical analog computing for image processing.Comment: Primary text 6 pages, 5 figures; Supplementary material 5 pages, 3
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