Tunable artificial vortex ice in nanostructured superconductors with a frustrated kagome lattice of paired antidots

Theoretical proposals for spin-ice analogs based on nanostructured superconductors have suggested larger flexibility for probing the effects of fluctuations and disorder than in the magnetic systems. In this paper, we unveiltheparticularitiesofavortexicesystembydirectobservationofthevortexdistributioninakagomelattice of paired antidots using scanning Hall probe microscopy. The theoretically suggested vortex ice distribution, lacking long-range order, is observed at half matching field (H1/2). Moreover, the vortex ice state formed by the pinned vortices is still preserved at 2H1/3. This unexpected result is attributed to the introduction of interstitial vortices at these magnetic-field values. Although the interstitial vortices increase the number of possible vortex configurations,itisclearlyshownthatthevortexicestateobservedat2H1/3islesspronetodefectsthanat H1/2. In addition, the nonmonotonic variations of the vortex ice quality on the lattice spacing indicates that a highly ordered vortex ice state cannot be attained by simply reducing the lattice spacing. The optimal design to observe defect-freevortexiceisdiscussedbasedontheexperimentalstatistics.Thedirectobservationsofatunablevortex ice state provides new opportunities to explore the order-disorder transition in artificial ice systems.