Identification and Enhancement of Kink Soliton Motions in a van der Waals Layer

Topological solitons, which connect degenerate ground states with phase shifts, have the potential to carry topologically protected information for dissipationless informatics. While topological solitons have been discussed actively in one-dimensional materials, a soliton with a geometric Z topology has been recently found in a van der Waals material of 1T-TaS₂ as a form of a mobile kink along domain walls in its charge-density-wave phase. However, details of kink kinetics and the mechanism of their motion have been obscured. Here, we reveal the kinetics and dynamics of kink solitons by tracking the motions of several kink solitons over a relatively long time using real-time scanning tunneling microscopy measurements. We disclose two different types of kink motions, that is, small (one unit cell) or large (a few unit cells) jumps. The energetics and atomistic details of kink jumps were revealed by density functional calculations. Furthermore, the average frequency of jumping modes is significantly enhanced by the injection of the tunneling current. Our work makes a step toward realizing control over the motion of kink solitons, which must be secured for soliton applications.