Light-Tunable Giant Anomalous Hall Effect in the Flat-Band Magnetic Weyl Semimetal $\mathrm{AlFe_2O_4}$

TL;DR

This study predicts that light can dynamically tune the giant anomalous Hall effect in the magnetic Weyl semimetal AlFe2O4 by manipulating its electronic structure, offering a pathway for ultrafast topological transport control.

Contribution

It introduces AlFe2O4 as a realistic material with flat bands and Weyl physics, and demonstrates light-induced control of its anomalous Hall effect through Floquet engineering.

Findings

AlFe2O4 exhibits a giant intrinsic AHC of 398 S·cm^{-1}.

Circularly polarized light suppresses effective electronic couplings.

Optical modulation enlarges Weyl node separation and suppresses AHC.

Abstract

Achieving a giant anomalous Hall effect (AHE) and enabling its effective tuning are fundamental goals for topological spintronics. Magnetic Weyl semimetals hosting flat bands offer a promising route to maximize the AHE. However, while theoretical models are well-established, realistic material candidates remain scarce. Since the intrinsic anomalous Hall conductivity (AHC) is topologically dictated by the momentum separation ($\kappa$) between Weyl nodes, actively manipulating remains a key challenge. Here, through comprehensive first-principles calculations, we establish the inverse spinel $\mathrm{AlFe_2O_4}$ as a realistic ferromagnetic half-metallic platform integrating three-dimensional flat bands and Weyl physics. Spin-orbit coupling induces a single pair of Weyl nodes, yielding a giant intrinsic AHC of $398\ \mathrm{S}\cdot\mathrm{cm}^{-1}$. By constructing a symmetry-constrained tight-binding model, we uncover a deterministic relationship between microscopic electronic couplings and the macroscopic AHE. Exploiting this via Floquet engineering with circularly polarized light, we demonstrate that the effective couplings are dynamically suppressed. This optical modulation controllably enlarges $\kappa$, shortens the topological Fermi arcs, and drives a dramatic, quantitative suppression of the AHC, providing a practical blueprint for ultrafast, light-controlled topological transport.