Topological phenomena on photonic crystal platform

The field of condensed matter theory has been advancing rapidly in recent years. This is particularly true for its topological branch, which applies the fairly abstract mathematical theory of topology to physical systems and has managed to predict a whole range of novel and exotic phenomena.

Still, despite great promise, applications and implementations are largely missing. This is owed to difficulties in realising such advanced novel concepts in atomic systems, which are restricted in both the flexibility and precision in designing them as well as characterisation by measurements. Artificial systems, such as crystals built from artificial atoms (also called "meta-atoms") made for light, may overcome such limitations and in the past decade strong progress has been made in understanding and engineering such systems with nearly arbitrary physical properties. Correspondingly, these two fields of photonic crystals and condensed matter may profit from a significant amount of cross-fertilisation.

In this project, we look at a set of topological effects and implement them in microwave systems to study them as well as harness them for applications. In particular, on the application side, we have proposed and studied exploiting the inherent robustness of topological effects to external perturbations for wireless power transfer. Moreover, artificial systems also allow unmatched experimental access to physical systems, meaning they allow the investigation of effects not observed in any other system so far. Here, we have looked at pseudomagnetism, which aims to use carefully engineered deformations in materials to mimic the effect of magnetic fields even on things, such as light, that do not carry change and hence could never be affected by real magnetic fields. This in turn gives access to a vast range of phenomena caused by and associated with such pseudomagnetic fields. However, progress has been slow which is caused in large parts by the fact that deterministically deforming a conventional crystalline material, such as for example graphene which was the first material that pseudomagnetic fields were studied in, is exceptionally difficult. Artificial materials like ours do not have these limitations and allow for the realisation of almost arbitrary deformations by suitable adaptation of the material design. Thus, we aim to observe and study these pseudomagnetic effects in such novel artificial platforms.

In summary, we want to use novel artificial materials engineered for electromagnetic radiation at microwave frequencies ("photonic crystals") to study and apply exotic physical phenomena from the theory of condensed matter.

This project falls within the EPSRC Physical Sciences research area. It involves a collaboration with Dr Charlie-Ray Mann (Institute of Photonic Sciences, Spain).