Metamaterials with broken symmetry and their applications

Conventionally, the development of optical technology has often relied on the discovery of new natural materials with desirable optical properties for specific tasks. Recently, instead of ‘discovering’ new materials, great efforts have been dedicated to ‘designing’ artificial materials, which are known as metamaterials. Optical metamaterials have anomalous optical properties beyond what are naturally available in their basic constituent materials, e.g., optical magnetism and negative refractive index. In this talk, I will give a few examples of metamaterials designed from the symmetry consideration. In the first example, a metamaterial with broken mirror symmetry was used to sort and route excitons in a monolayer MoS2 at room temperature. By exciton-surface plasmon coupling, the excitons of opposite chirality and their emissions were separated in real space and photon momentum space, respectively. In the second example, we explored the electric and magnetic dipole interaction in a meta-molecular with suitably designed symmetry. The magnetic and magneto-electric response in optical frequency was quantitively retrieved for the first time.