Ultrafast optical excitation of magnetic skyrmions

Abstract

Magnetic skyrmions in an insulating chiral magnet Cu2OSeO3 were studied by all-optical spin wave spectroscopy. The spins in the conical and skyrmion phases were excited by the impulsive magnetic field from the inverse-Faraday effect, and resultant spin dynamics were detected by using time-resolved magneto-optics. Clear dispersions of the helimagnon were observed, which is accompanied by a distinct transition into the skyrmion phase, by sweeping temperature and magnetic field. In addition to the collective excitations of skyrmions, i.e., rotation and breathing modes, several spin precession modes were identified, which would be specific to optical excitation. The ultrafast, nonthermal, and local excitation of the spin systems by photons would lead to the efficient manipulation of nano-magnetic structures.

Nonlinear Ultrafast Spin Scattering in the Skyrmion Phase of Cu2OSeO3

“…The initial excitation of the spin system occurs through spin-flip processes, which then decay into lower-energy excitations of the order parameter. The magnetic dispersion relations are anisotropic [30,31], and the observed dynamics in the x-ray scattering differ significantly from those in optical magnetic measurements of skyrmion materials [12,13], which measure dynamics of the q=0 magnetization. This indicates low-energy excitations that are not evident in measurements at the skyrmion/conical wave vectors.…”

“…Theoretical work predicts that the connected tetrahedron network in Cu 2 OSeO 3 gives rise to a Goldstone mode as well as other higher energy modes [10]. Microwave spectroscopy and optical pump-probe techniques have shown the presence of different collective modes such as circulating and breathing modes [11][12][13]. While these studies show that skyrmions exhibit interesting dynamic properties, more direct evidence of the effect of intense perturbative impulse on the skyrmion lattice can be obtained if we probe at the skyrmion q-vector using x-rays while pumping the system with an optical impulse.…”

Gyrotropic Skyrmion Modes in Ultrathin Magnetic Circular Dots

“…A number of associated extraordinary findings including emergent electromagnetic fields, topological Hall effect, ultralow densities of spin currents driving skyrmion motion, skyrmion breathing and rotation excitation modes etc. were reported in recent years [25][26][27][28][29][30][31][32] . Low and high frequency spin dynamics over a skyrmion background being of particular interest has been actively explored in 2D skyrmion lattices [26][27][28][29][30][31] .…”

“…were reported in recent years [25][26][27][28][29][30][31][32] . Low and high frequency spin dynamics over a skyrmion background being of particular interest has been actively explored in 2D skyrmion lattices [26][27][28][29][30][31] . Mochizuki 26 showed the existence of two in-plane rotational eigenmodes (clockwise and anticlockwise) of skyrmion spin texture unit cell and one breathing mode (oscillations of the skyrmion radius) in the GHz frequency range.…”

“…Mochizuki 26 showed the existence of two in-plane rotational eigenmodes (clockwise and anticlockwise) of skyrmion spin texture unit cell and one breathing mode (oscillations of the skyrmion radius) in the GHz frequency range. Later on, the experiments detecting internal skyrmion modes have been carried out [27][28][29][30][31] . However, the microwave measurements 27,28 confirmed the existence of only one of the skyrmion rotating modes and a breathing mode.…”