Rolling Motion of Rigid Skyrmion Crystallites Induced by Chiral Lattice Torque

Magnetic skyrmions
are topologically protected spin textures with
emergent particle-like behaviors. Their dynamics under external stimuli
is of great interest and importance for topological physics and spintronics
applications alike. So far, skyrmions are only found to move linearly
in response to a linear drive, following the conventional model treating
them as isolated quasiparticles. Here, by performing time and spatially
resolved resonant elastic X-ray scattering of the insulating chiral
magnet Cu2OSeO3, we show that for finite-sized
skyrmion crystallites, a purely linear temperature gradient not only
propels the skyrmions but also induces continuous rotational motion
through a chiral lattice torque. Consequently, a skyrmion crystallite
undergoes a rolling motion under a small gradient, while both the
rolling speed and the rotational sense can be controlled. Our findings
offer a new degree of freedom for manipulating these quasiparticles
toward device applications and underscore the fundamental phase difference
between the condensed skyrmion lattice and isolated skyrmions.