Controllable Topological Vortex Lattices
Some topological systems are attractive thanks to their resilience and ability to host quasiparticles useful for information storage. Researchers have fabricated topological systems using nanomagnet arrays and other metamaterials but have struggled to manipulate them. Now Cuiling Meng at the University of Colorado Boulder and her collaborators have fabricated a liquid-crystal-based topological system, called a combinatorial vortex lattice, that is easy to manipulate using laser tweezers [1]. Combinatorial vortex lattices could potentially be used not only to write and store information but also to perform logic operations, the researchers say.
To fabricate their combinatorial vortex lattices, the researchers confined a liquid crystal—a material composed of elongated rod-like organic molecules—in a cell made up of two glass slides. One glass slide promoted uniform molecule alignment, while the researchers shone blue light through the opposing slide to mark out a square lattice of pinning sites around which vortices could form. Because of the constraints imposed by the slides, the liquid crystal naturally formed bridge-like vortex lines that connected the adjacent vortex pinning sites. Since there are many possible degenerate ways for these connections to form, the low-energy rearrangement of adjacent vortex connections is possible using laser tweezers.
The team also created higher-energy vortex lines that connected nonadjacent sites from which vortices grow. These high-energy vortices possess an integer analogue of charge and are topological because the connections can’t be broken by simply rearranging neighboring pinning sites unless there is another vortex with the opposite charge nearby. The robustness of the topological charge could make higher-energy vortex lines suitable for storing information. What’s more, combinatorial vortex lattices are classical phenomena. Some topological notions that were once thought to be solely quantum have now found a classical correspondence, the researchers say.
–Martin Rodriguez-Vega
Martin Rodriguez-Vega is an Associate Editor for Physical Review Letters.
References
- C. Meng et al., “Emergent dimer-model topological order and quasiparticle excitations in liquid crystals: Combinatorial vortex lattices,” Phys. Rev. X 15, 021084 (2025).