Skyrmion generation via Laguerre-Gaussian beam irradiation in frustrated magnets

Abstract

Since its discovery, the study of magnetic skyrmions has been on the rise. In this paper, we discuss our investigations on the light-induced mechanisms for skyrmion generation in a centrosymmetric triangular magnetic lattice with competing $J_1$-$J_3$ interactions, and easy-axis anisotropy. We solve the stochastic Landau-Lifshitz-Gilbert equation for the lattice spin dynamics under Laguerre-Gaussian beam irradiation. Numerical results show that skyrmions are nucleated in two thermodynamic regions, each favoring different phases: the ferromagnetic phase and the skyrmion-lattice phase. In the ferromagnetic region, isolated skyrmions are generated mainly through stochastic thermal nucleation. In this regime, higher temperatures and larger beam widths are required to overcome the nucleation barrier. In contrast, in the skyrmion-lattice region, skyrmion nucleation occurs via thermal annealing, where the system relaxes toward its true ground state. These findings establish a comprehensive theoretical framework for optimizing optical control to generating light-induced skyrmionic textures in frustrated magnets.

Figures (13)

• Figure 1: Beam profiles at different $(p, m, w)$. The colors denote the local intensity at that site in the triangular lattice.
• Figure 2: Phase diagram at $T=0$, obtained through variational calculations leonov2015shizeng2016. A total of $201\times 201$ data points were generated, each comparing the energies of $6$ phases.
• Figure 3: An example of a skyrmion lattice from variational calculations at $a_1 = a_2 = 0.8$ and $\bar{m} = 0.2$.
• Figure 4: Time evolution of an isolated skyrmion at $A=0.7$ and $H=0.3$ with beam parameters $T_0=5$, $p=0$, $m=5$, and $w=10$. The white dashed circles at $t=50$ represent the upper and lower boundaries of the applied beam. The colorbar represents the out-of-plane spin component $S^z$.
• Figure 5: Probability maps at $A=0.7$ and $H=0.3, 0.4$, and $0.5$. The temperature is in units $J_1/k_{\mathrm{B}}$, while the beam width $w$ is in lattice unit $a$.