Topological photonics is a rapidly emerging field of research in which geometrical and
topological ideas are exploited to design and control the behavior of light. Drawing …

The study of classical wave physics has been reinvigorated by incorporating the concept of
the geometric phase, which has its roots in optics, and topological notions that were …

There have been significant recent advances in realizing band structures with geometrical
and topological features in experiments on cold atomic gases. This review summarizes …

Topology describes properties that remain unaffected by smooth distortions. Its main
hallmark is the emergence of edge states localized at the boundary between regions …

Abstract Parity–time (PT)-symmetric crystals are a class of non-Hermitian systems that allow,
for example, the existence of modes with real propagation constants, for self-orthogonality of …

We analyze chiral topological edge modes in a non-Hermitian variant of the 2D Dirac
equation. Such modes appear at interfaces between media with different “masses” and/or …

The topological properties of an object, associated with an integer called the topological
invariant, are global features that cannot change continuously but only through abrupt …

Geometric phases that characterize the topological properties of Bloch bands play a
fundamental role in the band theory of solids. Here we report on the measurement of the …

We present the first experimental observation of a topological transition in a non-Hermitian
system. In contrast to standard methods for examining topological properties, which involve …

Nonlinear topological photonics is an emerging field that aims to extend the fascinating
properties of topological states to a regime where interactions between the system …