Nonreciprocal Terahertz Beam Steering Manipulated by Magnetic Weyl Semimetal Metasurface Based on Universal Chirality‐ Wavevector‐ Magnetic Field Relation

Abstract Magnetic Weyl semimetal shows intriguing properties in both fundamental physics and potential applications. However, the complex relationship between nonreciprocal transmission and magnetic field manipulation in magnetic Weyl semimetal systems has not been generally clarified and fully utilized. Here, a universal Chirality–Wavevector–Magnetic field ( C ‐ K ‐ B ) relation is established in the magnetic Weyl semimetal system, which completely describes the spin topological band and its intrinsic polarization output in full space orientation under an arbitrary magnetic vector. This relation can provide complete guidance for the device design of nonreciprocal spin manipulation. Coupling this nonreciprocal mechanism with the photonic spin Hall effect of the geometric phased metasurface, a magnetic Weyl semimetal metasurface is constructed in the terahertz (THz) range, The experiments demonstrate the flexible THz beam steerings in a broad spatial dispersion range of ±25–±55° with four different working modes by only altering the biased magnetic vectors. Moreover, all these beam steering processes are accompanied by nonreciprocal isolating transmission with the isolation ratio reaching 27 dB. This C ‐ K ‐ B relation and active nonreciprocal beam steering devices are expected to prompt magneto‐optical devices and systems combined with echo isolation function in beam scanning, wavelength division multiplexing, and spin multiplexing.