Experimental evidence of proximity induced odd-frequency superconductivity in a topological insulator*

At an interface between a topological insulator (TI) and a conventional superconductor, the topological surface states have been predicted to rearrange in an interesting fashion. The induced superconductivity between an s-wave superconductor and a TI surface state is expected to develop a complex p-wave order parameter which may allow to create a Majorana Fermions inside the core of a vortex. These collective excitations are their own antiparticles and are the basic element in a proposal for fault-tolerant quantum computing. Here we present experimental evidence for proximity induced superconductivity in a thin layer of the TI Bi₂Se₃ grown on top of Nb. From depth-resolved measurements in the Meissner state, we observe a local enhancement of the magnetic field in Bi₂Se₃ that exceeds the externally applied field, thus supporting the existence of an intrinsic paramagnetic Meissner effect arising from an odd-frequency superconducting state.