4 research outputs found
Emergence Of Type-Ii Dirac Points In Graphynelike Photonic Lattices
We theoretically demonstrate that a type-II class of tilted Dirac cones can emerge in generalized two-dimensional anisotropic lattice arrangements. This is achieved by introducing a special set of graphynelike exchange bonds by means of which the complete spectrum of the underlying Weyl Hamiltonian can be realized. Our ab initio calculations demonstrate a unique class of eigensolutions corresponding to a type-II class of Dirac fermionic excitations. Based on our approach, one can systematically synthesize a wide range of strongly anisotropic band diagrams having tilted Dirac cones with variable location and orientation. Moreover, we show that asymmetric conical diffraction, as well as edge states, can arise in these configurations. Our results can provide a versatile platform to observe, for the first time, optical transport around type-II Dirac points in two-dimensional optical settings under linear, nonlinear, and non-Hermitian conditions
Genetic Optimization With Mixed-Order Prism Macroelements for 3-D Metamaterial Multilayered Structures
Bimorphic Floquet Topological Insulators
Topological theories have established a new set of rules that govern the
transport properties in a wide variety of wave-mechanical settings. In a marked
departure from the established approaches that induce Floquet topological
phases by specifically tailored discrete coupling protocols or helical lattice
motions, we introduce a new class of bimorphic Floquet topological insulators
that leverage connective chains with periodically modulated on-site potentials
to unlock new topological features in the system. In exploring a 'chain-driven'
generalization of the archetypical Floquet honeycomb lattice, we identify a
rich phase structure that can host multiple non-trivial topological phases
associated simultaneously with both Chern-type and anomalous chiral states.
Experiments carried out in photonic waveguide lattices reveal a unique and
strongly confined helical edge state that, owing to its origin in bulk flat
bands, can be set into motion in a topologically protected fashion, or halted
at will, without compromising its adherence to individual lattice sites.Comment: 17 pages, 7 figure