Tunable topological states hosted by unconventional superconductors with adatoms

Chains of magnetic atoms, placed on the surface of s-wave superconductors, have been established as a laboratory for the study of Majorana bound states. In such systems, the breaking of time reversal due to magnetic moments gives rise to the formation of in-gap states, which then hybridize to form one-dimensional topological superconductors. However, in unconventional superconductors even non-magnetic impurities can induce in-gap states since scattering of Cooper pairs changes their momentum but not their phase. Here, we propose a realistic path for creating topological superconductivity, which is based on an unconventional superconductor with a chain of non-magnetic adatoms on its surface. The system can be driven into a topological phase by tuning the magnitude and direction of an external Zeeman field, such that Majorana zero modes at its boundary can be generated, moved, and fused, paving the way towards braiding of Majorana zero modes.
To demonstrate the feasibility of this platform, we develop a general mapping of films with adatom chains to one-dimensional lattice Hamiltonians. This allows us to study unconventional superconductors such as Sr₂RuO₄ exhibiting multiple bands and an anisotropic order parameter.