Two-dimensional Shiba lattices as a platform for crystalline topological superconductivity

Localized or propagating Majorana boundary modes are the key feature of topological superconductors. They are rare in naturally-occurring compounds, but the tailored manipulation of quantum matter offers opportunities for their realization. Specifically, lattices of Yu-Shiba-Rusinov bound states – Shiba lattices – that arise when magnetic adatoms are placed on the surface of a conventional superconductor can be used to create topological bands within the superconducting gap of the substrate. I will show how scanning tunnelling microscopy is used to create and probe adatom lattices with single atom precision we reveal two signatures consistent with the realization of topological superconductors. One of the example strucutres I will discuss has edge modes as well as higher-order corner states, another example has symmetry-protected bulk nodal points. The topological character and boundary modes are protected by the spatial symmetries of the adatom lattice. Our results highlight the potential of Shiba lattices as a platform to design the topology and sample geometry of 2D superconductors.