Optically Driven Orbital Hall Transport in Floquet Odd-Parity Collinear Altermagnets with High Chern Numbers

Abstract

Recent studies have attracted increasing interest in nonrelativistic odd-parity magnetism and its associated topology in collinear altermagnets. Here, based on symmetry analysis and an effective model, we demonstrate that Floquet engineering can induce $f$-wave odd-parity altermagnetism in two-dimensional collinear antiferromagnetic multilayers via the coupling between circularly polarized light (CPL) and layer degrees of freedom. Furthermore, modifying the CPL induces nonequilibrium quantum anomalous Hall effect (QAHE) with tunable Chern numbers up to $C=\pm8$, arising from layer- and valley-dependent band inversions. The induced topological phase transitions provide an efficient means to manipulate the orbital Hall effect (OHE) by redistributing orbital angular momentum. First-principles calculations reveal that experimentally accessible VSi$_2$N$_4$ serves as a viable platform for topological phase diagram of the QAHE and OHE, featuring pronounced trigonal warping. Our findings establish a versatile route toward optically controllable topological phenomena, opening new opportunities for future developments in topological spintronics and orbitronics.

Figures (4)

• Figure 1: (a) and (b) Illustration of light-induced odd-parity AM in vdW AFM bilayes composed of FM monolayers with in-plane magnetization. The two sublattices with opposite spin polarization are depicted by antiparallel red and blue spin arrows. (c) Schematic illustration of the light-induced QAHE and light-modulated OHE. Red and blue spheres: sublattices with opposite spins. Orbiting orange and purple spheres: distinct OAM. Red and blue lines: direction and spin polarization of edge currents. (d) Spin-degenerate $H_{0}(\textbf{k})$ (black lines) and spin-resolved $H_{\rm{eff}}(\textbf{k})$ (red and blue circles) band structures.
• Figure 2: (a) Spin-resolved 3D band structures for the $f$-wave odd-parity AM state described by $H_{\rm{eff}}(\textbf{k})$. (b) Spin-layer-resolved band structure near the $K$ and $K'$ valley under RCPL with $\hbar\omega = 0.10$ eV at light intensity $eA/\hbar = 0.20~\mathrm{\AA}^{-1}$.(c) OHC as a function of energy for the equilibrium system and the nonequilibrium system driven by RCPL with different photon energies $\hbar\omega$ at $eA/\hbar = 0.20~\mathrm{\AA}^{-1}$. (d) The orbital-resolved band structures near the $K$ valley under different photon energies $\hbar \omega=0.1, 0.4, 0.5$ eV at $eA/\hbar = 0.20~\mathrm{\AA}^{-1}$.
• Figure 3: BC (left panel) and OBC (right panel) of the TB model in the $K$ valley under the RCPL with photon energy $\hbar\omega$ (a) $= 0.10$ eV, (b) $= 0.40$ eV and (c) $= 0.50$ eV. Total and layer-resolved AHC under the RCPL with photon energy $\hbar\omega$ (d) $= 0.10$ eV, (e) $= 0.40$ eV and (f) $= 0.50$ eV. The light intensity is $eA/\hbar = 0.20~\mathrm{\AA^{-1}}$. (g) OHC of the TB model under RCPL with $\hbar\omega =$$0.10$ eV and 0.50 eV as a function of light intensity $eA/\hbar$.
• Figure 4: (a) Crystal structure of the VSi$_2$N$_4$ bilayer. The gray region denotes the primitive cell. (b) The spin-resolved 3D band structures under RCPL. (c) Distribution of BC corresponding to the $C=-8$ QAH phase. (d) Phase diagram of band gap as functions of photon energy $\hbar\omega$ and light intensity $eA/\hbar$.