A significant fraction of topological phenomena (e.g., the quantum spin Hall effect, topological insulators, and Weyl semi-metals) can be explained through a Berry phase obtained from the theory of charge polarisation. The question of which novel properties will arise in the presence of higher-order multipolar terms has been a mystery for a long time, and just recently started to settle in the form of a theory of higher-order topological insulators. In spite of the theoretical advances, experimental demonstrations of such novel topological systems are still scarce. In this talk, I will discuss an experimental realization of a high-order topological phase, the quadrupole topological insulator, implemented in a phononic platform. This demonstration motivated the development of a systematic method for designing metamaterials, where the desired performance is first encoded in a tight-binding model, and then translated into a metamaterial geometry using an automated set of algorithms. Due to the ability of tight-binding models for capturing a diverse set of phenomena, we expect that our approach will enable a host of new materials and devices in the phononic and photonic fields.


Seminar, May 3, 2018, 12:00. ICFO’s Seminar Room

Hosted by Prof. Frank Koppens