Floquet-Engineering Weyl Points and Linked Fermi Arcs from Straight Nodal Lines

Abstract

Floquet engineering provides a powerful and flexible method for modifying the band structures of quantum materials. While circularly polarized light has been shown to convert curved nodal lines in three-dimensional semimetals into Weyl points, such a transformation is forbidden for an isolated straight nodal line. In this work, we uncover a dramatic shift in this paradigm when multiple straight nodal lines intersect. We observe that circularly polarized light not only gaps them into Weyl points but also induces unprecedented surface-state Fermi arcs that extend across the entire surface Brillouin zone and form a linked topological structure. These findings advance our fundamental understanding of light-driven transitions in topological semimetals and unveil a unique Weyl semimetal phase defined by linked Fermi arcs. We discuss potential exotic phenomena arising from this phase, applications of our predictions to spin-splitting antiferromagnets, and the extension of this Weyl semimetal phase to classical systems.

Figures (4)

• Figure 1: Schematic diagram illustrating the influence of CPL on different types of nodal lines. Dashed black lines denote gapped nodal lines, while solid dots represent CPL-induced FWPs of opposite chirality (red/blue). (a) CPL is incident along a general direction. (b) Two FWPs emerge from a circular nodal ring, displaced along $\boldsymbol{n}_{\parallel}$ (light’s in-plane projection). (c) No FWPs emerge for an isolated SNL. (d) Two FWPs appear near two SNLs’ crossing point, with their displacement vector generally non-parallel to $\boldsymbol{n}_{\parallel}$.
• Figure 2: (a) Red lines mark the locations of the SNLs before driving. (b) Configuration of the emergent FWPs in the driven system, with red and blue dots denoting FWPs of opposite chirality. Note that these FWPs at the top and bottom surfaces belong to the same group due to BZ periodicity. The layer Chern numbers are defined in these gapped planes (color-coded) away from the FWPs.
• Figure 3: (a) Momentum-dependence of layer Chern numbers. (b) Surface-state spectrum on the top $z$-normal surface. (c) Fermi arcs at zero energy (green and purple curves), with red and blue markers indicating Weyl-point projections. (d) Linked topology of Fermi arcs visualized on the surface BZ torus. Parameters are $eA_{0}=0.8$, $\omega=5$, $\eta=1$, $\theta=\pi/3$, and $\phi=\pi/3$.
• Figure 4: Zero-temperature Hall conductivity. (a) Hall conductivity $\sigma_{yz}$ as a function of the light's propagation direction, calculated for $\mu=0$ with parameter $eA_{0}=0.8$. (b) $\sigma_{yz}$ as a function of the light's intensity, with $\theta=\pi/3$, and $\phi=5\pi/6$. Common parameters are $\omega=5$, $\eta=1$, $V=0.1$, $\Gamma=0.2$, and $N_{x}\times N_{y}\times N_{z}=40\times40\times10$.