Partial chiral symmetry-breaking as a route to spectrally isolated topological defect states in two-dimensional artificial materials

Poli, Charles Joseph and Schomerus, Henning Ulrich and Bellec, Matthieu and Kuhl, Ulrich and Mortessagne, Fabrice (2017) Partial chiral symmetry-breaking as a route to spectrally isolated topological defect states in two-dimensional artificial materials. 2D Materials, 4 (2): 025008. ISSN 2053-1583

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Abstract

Bipartite quantum systems from the chiral universality classes admit topologically protected zero modes at point defects. However, in two-dimensional systems these states can be difficult to separate from compacton-like localized states that arise from flat bands, formed if the two sublattices support a different number of sites within a unit cell. Here we identify a natural reduction of chiral symmetry, obtained by coupling sites on the majority sublattice, which gives rise to spectrally isolated point-defect states, topologically characterized as zero modes supported by the complementary minority sublattice. We observe these states in a microwave realization of a dimerized Lieb lattice with next-nearest neighbour coupling, and also demonstrate topological mode selection via sublattice-staggered absorption.