Researchers Bo Leng and Vien Van from the University of California, Berkeley have made a significant advancement in the field of topological photonics. Their work, published in the journal Nature Photonics, explores the unique properties of flat-band states in two-dimensional (2D) Floquet topological photonic insulators, which could have practical applications in the energy sector, particularly in optical communications and data processing.
In their study, Leng and Van investigate the behavior of flat-band states in a 2D photonic Lieb lattice composed of coupled microring resonators. Unlike static tight-binding systems, where perfectly flat bands can only exist in topologically trivial phases, the researchers found that introducing periodic driving into the system allows for the existence of perfectly flat bands with nontrivial topology. This is characterized by a nontrivial quantized helicity, even though the quasi-energy bands have a zero Chern number.
The researchers tracked the evolution of the flat-band modes over each cycle and demonstrated that their non-Abelian displacements exhibit a helical motion. This motion can be described by a braiding of the world lines of their trajectories, with a nontrivial winding number directly connected to the helicity. The helical motion of the flat-band modes is a key finding, as it suggests that these systems can host non-Abelian topological states, which are typically challenging to realize in static systems.
To validate their theoretical findings, Leng and Van proposed an experimental scheme to measure the quantized non-Abelian helicity in a microring lattice subject to a synthetic magnetic field. This experimental approach could pave the way for practical applications in optical communications and data processing, where the manipulation of topological states of light could lead to more efficient and secure data transmission.
The results of this study suggest that Floquet topological photonic insulators based on coupled microring resonators can provide a versatile platform for investigating non-Abelian topological physics and strongly correlated phenomena in photonic flat-band systems. As the energy sector increasingly relies on optical technologies for data transmission and processing, the development of new materials and systems that can support nontrivial topological states of light could have significant implications for the future of energy technologies.
Source: Leng, B., & Van, V. (2023). Quantized non-Abelian helicity of flat bands in 2D Floquet topological photonic insulators. Nature Photonics.
This article is based on research available at arXiv.