Signature of proximity-induced p_x+ip_y triplet pairing in the doped topological insulator Bi₂Se₃ by the s-wave superconductor NbN

In the search for Majorana fermions in proximity-induced topological superconducting junctions, we happened to find a signature of same-spin triplet superconductivity which appears to dominate these elusive elementary excitations. Thin-film junctions and bilayers of the doped topological insulator Bi₂Se₃ and the s-wave superconductor NbN exhibit conductance spectra with coexisting prominent zero-bias and coherence peaks. Various tunneling models with different pair potentials have failed to fit our data, except for the triplet px + ipy pair potential, which breaks time-reversal symmetry, that yielded reasonably good fits. This provides supporting evidence for proximity-induced triplet superconductivity in the Bi₂Se ₃ layer near the interface with the NbN film.