Fig. 4: Simulations of high-order nonlinear magnonic correlations.
From: Extreme terahertz magnon multiplication induced by resonant magnetic pulse pairs
MNL(ωt, ωτ) for a the full-term calculation, b a calculation without DM interaction, D = 0, where the ground state has no spin canting, i. e., M = 0 in the ground state, and c a calculation without four-fold anisotropy in the Hamiltonian, K4 = 0. d MNL(ωt, ωτ) at fixed ωτ = ωAF. The full-term calculation (black line) is compared with simulations where the DM interaction is switched off (blue line) and the four-fold magnetic anisotropy is switched off (red line). e \({M}_{{{{{{{{{{\rm{NL}}}}}}}}}}}^{c}({\omega }_{t},\tau )\) at a fixed inter-pulse delay of τ = 4.8 ps. The result of the full quantum spin simulation (red line) is shown together with the result of the classical simulation (blue line). The quantum spin simulation yields stronger high-harmonic generation peaks (vertical dashed lines) compared to the classical simulation. Inset: Eigenenergies En of the unperturbed quantum spin Hamiltonian which has (2s+1)2 = 36 eigenstates for the studied two-site spin-s = 5/2 system. f Ratio between the strength of nth harmonic and fundamental harmonic generation peaks. The ratios extracted from the experimental mHHG spectrum in Fig. 1e (squares) are compared with the results of the quantum spin simulation (circles) and the classical simulation (rectangles).
