Aharonov-Bohm cages in photonic lattices

We report on the experimental realization of a uniform synthetic magnetic flux and the observation of Aharonov-Bohm cages in a rhombic photonic lattice of optical waveguides. In the regime where half a flux quantum is realized in each plaquette, all the energy bands collapse into nondispersive (flat) bands. The resulting localized eigenstates are then probed by studying the propagation of light in the bulk and at the edge of the photonic lattice. Our photonic lattice constitutes an appealing platform where the interplay between engineered gauge fields, frustration, localization, and topological properties can be finely studied. We further theoretically explore the localization properties of this system in the presence of interparticle mean-field interactions, which appear in photonic lattices as optical nonlinearities when increasing the light beam power. Surprisingly, we find that there still exist caged solutions and their nonlinear dynamics is accompanied with a breathing motion of the particle density reminiscent of a bosonic Josephson junction. Our results open an interesting route towards the characterization of nonlinear dynamics in flat band systems.

[1] Mukherjee et al., Phys. Rev. Lett. 121, 075502 (2018)
[2] Di Liberto et al., arXiv:1810.07641 (2018)