SELECTIVE ENHANCEMENT OF TOPOLOGICALLY PROTECTED MIDGAP STATE
Mercredi 23 juillet 2014
à 11h en salle C. Brot
Drawing on the concepts of topological band theory, I will describe how exponentially localized topologically protected midgap states form in photonic systems. I will apply concepts from passive non-Hermitian parity-time symmetry to demonstrate the selective control and enhancement of a topologically induced state in a one-dimensional microwave set-up. To conclude this part, I will extend the model to reveal the possibility of robust localized modes in 2D, created by lattice modulation only. Then, I will consider a strained honeycomb lattice in which inhomogeneous strain influences photon motion in a manner similar to an effective magnetic field. Focusing on a strain configuration which corresponds to a constant pseudomagnetic field, in the regime of pseudo-Landau level (pLL) formation, I will show that the degeneracy and spatial support of pLLs systematically depend on the geometry of the system. These features are dictated by algebraic constraints in the atomistic theory, and signify a departure from the standard picture. In addition, in connection with the first part of the talk, I will show that the introduction of vortices in the honeycomb lattice leads to the appearance of localized midgap states.
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