Majorana Bound States in Chains of Superconducting Islands

The differential conductance is calculated for charge tunneling into a semiconductor wire proximity coupled to several superconducting islands. Alone the islands are too small to host well separated Majorana bound states, however, together strong topological protection can arise. The topological phase boundary is studied with respect to the magnetic field, chemical potential, and coupling between the islands. It is shown that the onset of the topological phase has a non-trivial dependence on the island coupling.