Octupole corner state in a three-dimensional topological circuit

Higher-order topological insulators featuring quantized bulk polarizations and zero-dimensional corner states are attracting increasing interest due to their strong mode confinement. Recently, scientists from China and the UK demonstrated in a 3-D topological circuit the existence of an octupole corner state, which is induced by the octupole moment of the bulk circuit and topologically protected by three anticommuting reflection symmetries. This work is not only of fundamental importance but als...