Floquet Weyl Phases in a Three Dimensional Network Model

TL;DR

This paper explores 3D Floquet bandstructures in a network model, revealing Weyl phases with Fermi arc surface states and topological phase transitions, which can be experimentally realized in electromagnetic networks.

Contribution

It demonstrates the existence of Weyl phases in 3D Floquet network models and links their topology to gapped phase transitions, extending topological phenomena known from 2D systems.

Findings

Weyl phases exhibit Fermi arc surface states.

Tuning network parameters induces topological phase transitions.

Weyl point trajectories relate to gapped phase topology.

Abstract

We study the topological properties of 3D Floquet bandstructures, which are defined using unitary evolution matrices rather than Hamiltonians. Previously, 2D bandstructures of this sort have been shown to exhibit anomalous topological behaviors, such as topologically-nontrivial zero-Chern-number phases. We show that the bandstructure of a 3D network model can exhibit Weyl phases, which feature "Fermi arc" surface states like those found in Weyl semimetals. Tuning the network's coupling parameters can induce transitions between Weyl phases and various topologically distinct gapped phases. We identify a connection between the topology of the gapped phases and the topology of Weyl point trajectories in k-space. The model is feasible to realize in custom electromagnetic networks, where the Weyl point trajectories can be probed by scattering parameter measurements.