Floquet chiral hinge modes and their interplay with Weyl physics in a three-dimensional lattice

TL;DR

This paper explores how a three-dimensional Floquet lattice can host chiral hinge states that coexist with Weyl surface states, revealing their robustness and potential realization with ultracold atoms.

Contribution

It introduces a model demonstrating Floquet chiral hinge modes coexisting with Weyl physics, highlighting their robustness and unique boundary reflection mechanisms.

Findings

Chiral hinge modes coexist with Weyl surface states in the model.

Hinge modes are robust against local defects and parameter variations.

Implementation with ultracold atoms in optical superlattices is feasible.

Abstract

We demonstrate that a three dimensional time-periodically driven (Floquet) lattice can exhibit chiral hinge states and describe their interplay with Weyl physics. A peculiar type of the hinge states are enforced by the repeated boundary reflections with lateral Goos-H\"{a}nchen like shifts occurring at the second-order boundaries of our system. Such chiral hinge modes coexist in a wide range of parameters regimes with Fermi arc surface states connecting a pair of Weyl points in a two-band model. We find numerically that these modes still preserve their locality along the hinge and their chiral nature in the presence of local defects and other parameter changes. We trace the robustness of such chiral hinge modes to special band structure unique in a Floquet system allowing all the eigenstates to be localized in quasi-one-dimensional regions parallel to each other when open hinge boundaries are introduced. The implementation of a model featuring both the second-order Floquet skin effect and the Weyl physics is straightforward with ultracold atoms in optical superlattices.