# Helically Magnetized Plasma: From Photonic Fermi‐Arc Metal to Chirality‐Free Uniaxial Medium

## TL;DR

Researchers use a helically magnetized plasma to create a photonic Fermi-arc metal, enabling new insights into topological transitions and potential photonic devices.

## Contribution

A novel optical realization of Fermi-arc metals in magnetized plasma with full analytical tracking of Weyl node evolution.

## Key findings

- Fermi-arc metal state is realized and manipulated in a real system under slowly varying modulation.
- Opposite-chirality Fermi arcs hybridize and recombine as modulation increases, eliminating chirality without conventional node annihilation.
- A chirality-free uniaxial optical medium is achieved, revealing global topological transitions in nonuniform Weyl systems.

## Abstract

Fermi‐arc metals, unconventional semi‐metals featuring cylindrical Fermi surfaces formed by Fermi arcs, have recently attracted extensive attention for realizing a novel metallic phase that retains chiral anomaly responses yet suppresses quantum oscillations. Although it was proposed that spatially twisting a superlattice of thin Weyl metals can form a Fermi‐arc metal, previous local‐approximation analyses are valid only for slowly varying systems and cannot capture all rich physics in such systems. Here, we report an optical realization of such a phase in a natural magnetized plasma subjected to a helically modulated magnetic field. Unlike previous studies on artificial heterostructure platforms, we admit a fully analytical, nonperturbative treatment that tracks a complete evolution of Weyl node. In the slowly varying regime, our platform faithfully realizes and manipulates the Fermi‐arc metal state in a real system. As the modulation rate increases, Fermi‐arcs inheriting opposite chiralities start to hybridize. Remarkably, in the deep nonperturbative limit, chirality vanishes, not through the conventional Weyl point annihilations, but via Fermi arc recombination, resulting in a chirality‐free uniaxial optical medium. These findings unveil global topological transitions in nonuniform Weyl systems and open routes toward photonic devices based on engineered Fermi‐arc dynamics.

A helically modulated magnetic field in magnetized plasma realizes a photonic Fermi‐arc metal, enabling full analytical tracking of Weyl node evolution. As modulation strengthens, opposing‐chirality Fermi arcs hybridize and recombine, yielding a chirality‐free uniaxial optical medium without conventional node annihilation. This reveals global topological transitions in nonuniform Weyl systems and unveils new pathways for photonic devices harnessing engineered Fermi‐arc dynamics.