Gauge Field Induced Chiral Zero Mode in Five-dimensional Yang Monopole Metamaterials

TL;DR

This paper demonstrates the experimental realization of a chiral zero mode in a five-dimensional topological system using metamaterials, revealing new ways to control electromagnetic waves through higher-dimensional topological effects.

Contribution

It introduces a method to couple a Yang monopole with an external gauge field in a metamaterial, experimentally demonstrating a gapless chiral zero mode in a five-dimensional topological setting.

Findings

Existence of a gapless chiral zero mode in a five-dimensional system.

Control of gauge fields using metallic helical structures in metamaterials.

Intrinsic connection between different dimensional topological systems.

Abstract

Owing to the chirality of Weyl nodes characterized by the first Chern number, a Weyl system supports one-way chiral zero modes under a magnetic field, which underlies the celebrated chiral anomaly. As a generalization of Weyl nodes from three-dimensional to five-dimensional physical systems, Yang monopoles are topological singularities carrying nonzero second-order Chern numbers c2 = +1 or -1. Here, we couple a Yang monopole with an external gauge field using an inhomogeneous Yang monopole metamaterial, and experimentally demonstrate the existence of a gapless chiral zero mode, where the judiciously designed metallic helical structures and the corresponding effective antisymmetric bianisotropic terms provide the means for controlling gauge fields in a synthetic five-dimensional space. This zeroth mode is found to originate from the coupling between the second Chern singularity and a generalized 4-form gauge field - the wedge product of the magnetic field with itself. This generalization reveals intrinsic connections between physical systems of different dimensions, while a higher dimensional system exhibits much richer supersymmetric structures in Landau level degeneracy due to the internal degrees of freedom. Our study offers the possibility of controlling electromagnetic waves by leveraging the concept of higher-order and higher-dimensional topological phenomena.