Domain wall motion in a polycrystalline vortex lattice
Disorder fundamentally reshapes how crystalline systems respond to external forces, yet it remains unclear whether disorder drives interacting lattices toward glassy states or instead fragments them into domains separated by mobile interfaces. Here, we investigate vortex motion in superconducting island arrays, where disorder is introduced in a controlled manner by tuning the magnetic field away from commensurate vortex fillings. By driving vortices with an applied current, we observe a two-step depinning transition at incommensurate fillings. Comparison with molecular vortex model simulations shows that this intermediate regime is consistent with domain wall motion in a polycrystalline vortex lattice. While two-step depinning has been explored theoretically in driven periodic systems, direct experimental evidence linking this behavior to interface-dominated vortex motion has been lacking. Our results demonstrate that disordered, interacting vortex systems with strong periodic pinning can favor interface physics over homogeneous glassy dynamics.