Topological Transitions in Metamaterials

Manipulating Optical Topology Phase transitions in solid-state systems are often associated with a drastic change in the properties of that system. For example, metal-to-insulator transition or magnetic-to-nonmagnetic states find wide application in memory storage technology. An exotic electronic phase transition is the Lifshitz transition, whereby the Fermi surface undergoes a change in topology and a drastic change in the electronic density of states. Krishnamoorthy et al. (p. 205) now show that the notion of such a phase transition can be carried over to the optical regime by the suitable design of a metamaterial structure. This effect could be used to control the interaction between light and matter. Metamaterials can undergo an optical analog of electronic phase transitions that impacts local light-matter interactions. Light-matter interactions can be controlled by manipulating the photonic environment. We uncovered an optical topological transition in strongly anisotropic metamaterials that results in a dramatic increase in the photon density of states—an effect that can be used to engineer this interaction. We describe a transition in the topology of the iso-frequency surface from a closed ellipsoid to an open hyperboloid by use of artificially nanostructured metamaterials. We show that this topological transition manifests itself in increased rates of spontaneous emission of emitters positioned near the metamaterial. Altering the topology of the iso-frequency surface by using metamaterials provides a fundamentally new route to manipulating light-matter interactions.