Antichiral topological phases and protected bulk transport in dual-helix Floquet lattices

Abstract

The incorporation of driven auxiliary nodes in Floquet lattices can substantially enhance their topological nature, resulting in unique nontrivial phases. Here, we develop an alternative design approach in Floquet topology by introducing a dual-helix modulation scheme that can simultaneously support a clockwise and a counterclockwise helicity in a singular unit cell. As a result, the band structure of a dual-helix configuration can parametrically deform between a conventional phase that exhibits crossed edge states and an antichiral phase with tilted unidirectional states, showcasing for the first time an antichiral phase in Floquet topological systems. An extended family of tilted and overtilted edge states is identified and topologically characterized, revealing that integer Chern and winding numbers can successfully characterize lattices that lack global topological gaps. This results in a rich dynamic response where light wave-packets can acquire different velocities at adjacent edges, and even halt or reverse their direction into unidirectional bulk channels, preserving their topological protection. To investigate these effects, we study a dual-helix photonic lattice of evanescently coupled waveguides where a nontrivial topology can now emerge on a completely stationary configuration, departing from conventional schemes that require helical variations of the lattice sites.