Theoretical seminar | 11 May 2022

Topological waves in non-reciprocal scattering networks

We study the topological properties of waves propagating in non-reciprocal scattering networks. Such networks, made of multiport non-reciprocal components connected by reciprocal transmission lines, can support three distinct topological phases: a trivial insulating phase, a Chern topological phase, and an extra anomalous topological phase. We will discuss, using simple graph theory arguments, the origin of the anomalous phase, and highlights its fundamental differences with the Chern phase. Using numerical studies and microwave experiments, we will demonstrate the superior robustness of anomalous edge transport over Chern edge transport, for various types of disorder, from random phase delays, to scattering and amorphous disorder. We will conclude on the potential applications of such networks in microwaves.

Zhang, Z., Delplace, P. & Fleury, R. Superior robustness of anomalous non-reciprocal topological edge states. Nature 598, 293–297 (2021).