Polariton ℤ Topological Insulator.

We demonstrate that honeycomb arrays of microcavity pillars behave as an optical-frequency twodimensional photonic topological insulator. We show that the interplay between the photonic spin-orbit coupling natively present in this system and the Zeeman splitting of exciton polaritons in external magnetic fields leads to the opening of a nontrivial gap characterized by a C = ±2 set of band Chem numbers and to the formation of topologically protected one-way edge states. [ABSTRACT FROM AUTHOR]