Rolling Motion of Rigid Skyrmion Crystallites Induced\nby Chiral Lattice Torque

Magnetic skyrmions\nare topologically protected spin textures with\nemergent particle-like behaviors. Their dynamics under external stimuli\nis of great interest and importance for topological physics and spintronics\napplications alike. So far, skyrmions are only found to move linearly\nin response to a linear drive, following the conventional model treating\nthem as isolated quasiparticles. Here, by performing time and spatially\nresolved resonant elastic X-ray scattering of the insulating chiral\nmagnet Cu<sub>2</sub>OSeO<sub>3</sub>, we show that for finite-sized\nskyrmion crystallites, a purely linear temperature gradient not only\npropels the skyrmions but also induces continuous rotational motion\nthrough a chiral lattice torque. Consequently, a skyrmion crystallite\nundergoes a rolling motion under a small gradient, while both the\nrolling speed and the rotational sense can be controlled. Our findings\noffer a new degree of freedom for manipulating these quasiparticles\ntoward device applications and underscore the fundamental phase difference\nbetween the condensed skyrmion lattice and isolated skyrmions.