Fig. 3: Mechanism of light-driven DWs.
From: High-speed antiferromagnetic domain walls driven by coherent spin waves
a Schematic of Néel-type DW at different times (t0, t1, t2) after clockwise rotations of n for negative (left panel) and positive (right panel) winding number. b Schematic of coherent in-plane magnon induced by a circularly polarized laser pulse. m1 and m2 indicate the sublattice moments and mz is the out-of-plane moment induced by laser. The Néel vector n = (m2 − m1)/2 initially rotates in the clockwise direction and its full trajectory is a back-and-forth oscillation in the xy plane (inset). c SHG transients for linear pump excitation with the probe beam linearly polarized in the \(\hat{x}\) (circular markers) or \(\hat{y}\) (square markers) direction, giving SHG proportional to \({n}_{y}^{2}\) or \({n}_{x}^{2}\) respectively. The black curves are guides to the eye. d Same as c but with circularly polarized pump. The black curves are fitted to the square of a damped sine wave: \({I}_{{{{\rm{SHG}}}}}={I}_{0}{(\sin (2\pi ft+{\phi }_{0}){e}^{-t/\tau })}^{2}\), where I0 is the intensity, f is the frequency of oscillation, ϕ0 is a phase offset, and τ is the decay time constant. e Extracted change in Néel vector angle, Δϕ(t), using the case of circular pump with \(\hat{x}\) probe in d. Since the SHG cannot distinguish between positive and negative Δϕ, we have chosen the signs of the data to give agreement with f ≈ 2.8 GHz found in d. The black curve is a fit to a damped sine wave.
