Monopole topological resonators

Abstract

Among the many far-reaching consequences of the potential existence of a magnetic monopole, it induces topological zero modes in the Dirac equation, which were derived by Jackiw and Rebbi 46 years ago and have been elusive ever since. Here, we show that the monopole and multi-monopole solutions can be constructed in the band theory by coupling the three-dimensional Dirac points in hedgehog spatial configurations through Dirac-mass engineering. We then experimentally demonstrate such a monopole bound state in a structurally-modulated acoustic crystal as a cavity device. These monopole resonators not only support an arbitrary number of degenerate mid-gap modes, but also offer the optimal single-mode behavior possible -whose modal spacing is inversely proportional to the cubic root of the modal volume. Our work completes the kink-vortex-monopole trilogy of zero modes and provides the largest free spectral range for sizable resonators.

Realization of a three-dimensional photonic higher-order topological insulator

“…The ability to integrate 2D surface states, 1D hinge states, and 0D corner states in a single photonic structure may yield potential applications for multidimensional photon steering in 3D photonic devices. Since our work provides a versatile platform for directly mimicking 3D tight-binding models in 3D photonic crystals, we envision more experimental studies on realizing topological lattice defects such as dislocation [76][77][78], disclination [79], and Dirac vortex [80][81] in 3D photonic crystals. Along these lines, 3D photonic topological insulators and HOTIs operating at telecom or visible frequencies are on the horizon [82][83].…”