Size-dependence of vortex shells in mesoscopic superconducting disks

In recent experiments on direct vortex visualization using the Bitter decoration technique, vortex shells were revealed in mesoscopic superconducting Nb disks with radii R∼1R∼1 to 2.5 μm. Some of the observed vortex configurations did not agree with earlier theoretical predictions. We show that this discrepancy is due to the effect of the London screening in rather large disks (i.e., R>λR>λ), while in previous theoretical studies smaller disks (R≪λ(R≪λ) were analyzed, and the screening effects were disregarded. Thus we found that the radius of the superconducting disk has a pronounced influence on the vortex configuration in contrast to, e.g., the case of parabolic confined charged particles, and we obtained the missing vortex configurations in agreement with the experiment.