Nature Nanotech. 9, 710–715 (2014)

Geometrical frustration emerges when it is impossible to arrange a set of particles in a way that minimizes their pairwise interactions. Engineering such systems artificially provides the ultimate probe of these exotic frustrated ice-like states. In this respect, superconductors make great model systems — their vortices (magnetic flux quanta) act as the particles, and non-superconducting islands are used to define the underlying geometry.

One limitation of this approach is that any modification requires the fabrication of a new device. But Juan Trastoy and colleagues have now devised a way to circumvent this problem, by etching defects close enough together to overcome the potential barrier between them. This effectively allows temperature to control the energy landscape, offering a means of modifying ice formation in real time.

The team were able to show that for various island arrangements, the vortices formed frustrated states, which were then thawed by increasing the temperature. The analogy with regular ice could hardly be more apt.