## Seminar

### Metamaterial approach towards topological photonics

**Speaker: Shuang Zhang (Birmingham)**

**Date: Wednesday 24 October 2018**

**Time: 15:00**

**Venue: Queens Buildings N/3.28**

Metamaterials have attracted tremendous attention due to their exotic optical properties and functionalities that are not attainable from naturally occurring materials [1]. In particular, metamaterials can be designed to introduce strong spin-orbit coupling for light and consequently nontrivial topological properties. In this talk, I will start with a brief introduction to the concepts of Berry curvature, Chern number and topological photonics. I will show that combination of chirality [2, 3] and hyperbolicity – an extreme form of anisotropy [4], can result in nontrivial topological orders in metamaterials and consequently topologically protected photonic surface states that are immune from scattering by defects and sharp edges [5]. The Weyl points in such systems result from the crossing between the bulk longitudinal plasmon mode and the transverse circularly polarized propagating modes [6]. The photonic ‘Fermi arcs’ were directly observed in the microwave regime [7], which showed Riemann-surface like helicoid configuration in the energy-momentum space [8]. I will further introduce a metamaterial approach for realizing three dimensional Dirac points, each of which represents the merging of two Weyl points with opposite chiralities. Spin polarized Fermi arcs are supported at the surface of the Dirac metamaterial