A conventional topological insulator (TI) has gapped bulk states but gapless edge states.
The emergence of the gapless edge states is dictated by the bulk topological invariant of the …

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 …

Abstract Higher-order topological insulators,,,–are a family of recently predicted topological
phases of matter that obey an extended topological bulk–boundary correspondence …

Topological systems are inherently robust to disorder and continuous perturbations,
resulting in dissipation-free edge transport of electrons in quantum solids, or reflectionless …

The mathematical field of topology has become a framework in which to describe the low-
energy electronic structure of crystalline solids. Typical of a bulk insulating three …

The studies of topological phases of matter have been developed from condensed matter
physics to photonic systems, resulting in fascinating designs of robust photonic devices …

Recently, higher-order topological phases that do not obey the usual bulk-edge
correspondence principle have been introduced in electronic insulators and brought into …

Photonic topological insulators enable topological boundary modes that are resilient to
defects and disorder, irrespective of manufacturing precision. This property is known as …

A d-dimensional second-order topological insulator (SOTI) can host topologically protected
(d-2)-dimensional gapless boundary modes. Here, we show that a 2D non-Hermitian SOTI …

We study surface states of topological crystalline insulators and superconductors protected
by inversion symmetry. These fall into the category of “higher-order” topological insulators …