Size effect in the vortex-glass transition in submicron ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{y}}$ strips: Evidence for softening of vortex matter

The I-V curves of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathit{y}}$ strips, with widths of 0.54 to 5.6 μm, were measured in magnetic fields. All the strips showed critical scaling behavior, and a clear decrease in the vortex-glass (VG) transition temperature with decreasing width was observed. This finding proves that the interaction range of vortices is relevant in characterizing the phase transition, and that softening of the vortex-matter elasticity occurs upon approaching this scale. Moreover, the results are not easily explained by the flux-creep picture and give strong support to the VG picture.