  We report dynamics of skyrmion bubbles driven by spin-transfer torque in
achiral ferromagnetic nanostripes using micromagnetic simulations. In a
three-dimensional uniaxial ferromagnet with a quality factor that is smaller
than 1, the skyrmion bubble is forced to stay at the central nanostripe by a
repulsive force from the geometry border. The coherent motion of skyrmion
bubbles in the nanostripe can be realized by increasing the quality factor to
~3.8. Our results should propel the design for future spintronic devices such
as artificial neural computing and racetrack memory based on dipole-stabilized
skyrmion bubbles.
