Infrared Quantum Magneto-Optical Transport in Magnetic Weyl Semimetals RAlGe (R = La, Ce, Pr)

Weyl semimetals (WSMs) have garnered significant theoretical and experimental interest due to their unique topological properties and exotic quantum states. These materials host massless, chiral Weyl fermions, leading to novel phenomena such as negative magneto-resistance, Fermi arcs, and anomalous Hall effects. Magnetic Weyl semimetals (MWSMs) introduce an additional layer of complexity, as their properties depend on magnetic texture and phase, offering new avenues for control over their topological characteristics. However, experimental verification of Weyl physics remains challenging due to competing classical effects and limitations in conventional measurement techniques. In this work, the interplay between the magnetic ordering of PrAlGe and a possible topological transition is observed indirectly in a chiral photovoltaic experiment. We investigate the optical reflectivity of MWSM candidates in the mid-infrared (MIR) regime to explore their magneto-optical behavior. Given the proximity of Weyl nodes to the Fermi level, a clean spectral distinction of Weyl-related phenomena necessitates extending these studies into the far-infrared (FIR) region, a notoriously tricky spectral range for conventional optics. To address this challenge, we propose and demonstrate a novel MIR metasurface device with a design principle that can be extended to the FIR regime. This work provides insight into the optical properties of MWSMs and lays the foundation for future studies employing FIR polarimetry to probe topological materials.