Observation of non-Abelian band topology without time-reversal symmetry

TL;DR

This paper demonstrates the realization of non-Abelian band topology in systems without time-reversal symmetry, using Kagome lattices and gyromagnetic photonic crystals to manipulate complex topological states and edge modes.

Contribution

It introduces the first experimental observation of non-Abelian topological physics in T-broken systems, expanding the scope beyond T-symmetric materials.

Findings

Observation of multigap antichiral edge states

Control of non-Abelian band nodes via magnetic flux tuning

Splitting quadratic points into Dirac points

Abstract

Going beyond the conventional theory, non-Abelian band topology uncovers the global quantum geometry of Bloch bands with multiple gaps and thus unveil a new paradigm for topological physics. However, to date, all non-Abelian topological materials are restricted to systems with time-reversal symmetry (T). Here, starting from a Kagome lattice inspired by Haldane model and designer gyromagnetic photonic crystals (PhCs), we show that T breaking can lead to rich non-Abelian topological physics, particularly the emergence of multigap antichiral edge states. Simply changing the magnetic flux of the Kagome lattice, or in-situ tuning the local magnetic field of the gyromagnetic PhCs, can lead to the unconventional creation, braiding, merging, and splitting of non-Abelian charged band nodes, alongside with the direct manipulation of the multigap antichiral edge states. Particularly, the quadratic point can be split into four Dirac points, a phenomenon unique in T-broken systems. Our theoretical and experimental findings will inspire a new direction in the study of non-Abelian physics in T-broken systems and open an unprecedent pathway for topological manipulation of electromagnetic waves.