  Using atomistic magnetic simulations we investigate the soliton motion along
a pinned skyrmion chain containing an interstitial skyrmion. We find that the
soliton can exhibit stable motion along the chain without a skyrmion Hall
effect for an extended range of drives. Under a constant drive the solitons
have a constant velocity. We also measure the skyrmion velocity-current curves
and identify the signatures of different phases including a pinned phase,
stable soliton motion, and quasi-free motion at higher drives where all of the
skyrmions depin from the pinning centers and move along the rigid wall. In the
quasi-free motion regime, the velocity is oscillatory due to the motion of the
skyrmions over the pinning sites. For increasing pinning strength, the onset of
soliton motion shifts to higher values of current density. We also find that
for stronger pinning, the characteristic velocity-current shape is affected by
the annihilation of single or multiple skyrmions in the drive interval over
which the soliton motion occurs. Our results indicate that stable skyrmion
soliton motion is possible and could be useful for technological applications.
