Proposed detection of the topological phase in ring-shaped semiconductor-superconductor nanowires using Coulomb blockade transport.

In semiconductor-superconductor hybrid structures a topological phase transition is expected as a function of the chemical potential or magnetic field strength. We show that signatures of this transition can be observed in nonlinear Coulomb blockade transport through a ring shaped structure. In particular, on the scale of the superconducting gap and for a fixed electron parity of the ring, the excitation spectrum is independent of flux in the topologically trivial phase but acquires a characteristic h/e periodicity in the nontrivial phase. We relate the h/e periodicity to the recently predicted 4π periodicity of the Josephson current across a junction formed by two topological superconductors.