Photonic emulation of two-dimensional materials with antiferromagnetic order

The work introduces an electromagnetic metamaterial called a spin-valley photonic topological insulator (SV-PTI). It is designed to emulate a broad class of theoretically predicted gapped two-dimensional materials that have antiferromagnetic order coupled to the valley degree of freedom. Using first-principles electromagnetic simulations and an analytic model, the authors show that propagation of chiral states at the interface between two SV-PTIs is governed by a single controlling parameter. This parameter determines the group velocity, polarization, and whether topological protection is present. The abstract further explains that the presence or absence of topological protection depends on the geometry of the line of least frequency separation between the bandgap-forming propagation bands. The authors state that controlling group velocity enables topologically-protected compression of electromagnetic energy.