Local and Non-local Transport Measurements in Bi₂Se₃-Nb-Bi₂Se₃ Heterostructures

The interplay of superconductivity (S) with spin-momentum locked surface states in topological insulators (TI) is predicted to host exotic electronic excitations that exhibit the properties of Majorana fermions. We report the results of measurements on TI-S-TI devices consisting of a superconducting Nb strip contacted on its edges by two opposing Bi₂Se₃ leads that serve as current injectors. Local resistance measurements show gap-like features, a zero-bias resistance peak, and a sharp change of resistance at high bias voltages. The non-local resistance exhibits features that mirror the gap-like structure in the local resistance and an asymmetry with respect to the local and non-local bias current, suggesting that the nature of the non-local transport depends on the spin of the injected carriers. Our results will be discussed in the context of unconventional superconductivity and non-equilibrium spin relaxation in the superconductor.