Photonic Jackiw-Rebbi states in all-dielectric structures controlled by bianisotropy

Abstract

Electric and magnetic resonances of dielectric particles have recently uncovered a range of exciting applications in steering of light at the nanoscale. Breaking of particle inversion symmetry further modifies its electromagnetic response giving rise to bianisotropy known also as magneto-electric coupling. Recent studies suggest the crucial role of magneto-electric coupling in realization of photonic topological metamaterials. To further unmask this fundamental link, we design and test experimentally one-dimensional array composed of dielectric particles with overlapping electric and magnetic resonances and broken mirror symmetry. Flipping over half of the meta-atoms in the array, we observe the emergence of interface states providing photonic realization of the celebrated Jackiw-Rebbi model. We trace the origin of these states to the fact that local modification of particle bianisotropic response affects its effective coupling with the neighboring meta-atoms which provides a promising avenue to engineer topological states of light.

Photonic Topological States Mediated by Staggered Bianisotropy

“…As a specific platform to implement the proposed system, we use dielectric disks made from commercially available high‐permittivity ceramics with real and imaginary parts of permittivity and , respectively, in 1 − 3 GHz frequency range. Note that this level of losses is essentially higher than that available for microwave ceramics [ 23 ] and considered here to highlight the robustness of the predicted topological states. By tuning the aspect ratio of the disk, we ensure that electric and magnetic dipole resonances for in‐plane dipoles overlap.…”

“…However, the previous studies [ 10,15–18,20–23 ] focused only on the case of uniform bianisotropy which was used as a mechanism to open a topologically nontrivial bandgap. Specifically, those works investigated either edge or interface states at the boundary between the two domains with the opposite signs of magneto‐electric coupling.…”

“…[ 24 ] In this case, the sign of bianisotropy and the magnitude of the coupling parameter can easily be altered by flipping the disk, as illustrated in Figure a. Exploiting such strategy, we design the arrays depicted in Figure 1b,c featuring an alternating pattern of effective coupling constants and supporting the topological modes at the edge and interface in contrast to the topologically trivial 1D structure of identical bianisotropic disks, [ 23 ] which supports only Jackiw‐Rebbi‐type state bound to the interface between the two halves of the array with the opposite signs of bianisotropy.…”

Doublons, topology and interactions in a one-dimensional lattice

“…The field continues to display some fascinating physics, from unidirectional propagation of optical states immune to disorder [4], to the development of topological lasers [5], to the creation of topologically-protected quantum light [6,7]. The simplicity and beauty of the field has ensured that many theoretical works do not need to stray beyond the single-particle level in order to describe and predict some fascinating topological photonic effects [8][9][10][11]. This is especially true when considering phenomena in photonic lattices inspired by iconic topological theories, such as the Harper-Hofstadter [12], Su-Schrieffer-Heeger [13] and Haldane models [14].…”

Photonic topological states mediated by staggered bianisotropy

“…However, the previous studies [11][12][13][14][16][17][18][19][20] focused only on the case of uniform bianisotropy which was used as a mechanism to open topologically nontrivial bandgap. Specifically, those works investigated either edge or interface states at the boundary between the two domains with the opposite signs of magneto-electric coupling.…”