Nonreciprocal Switching Currents in Superconductor/Semiconductor Heterostructure Devices

Superconductor-Semiconductor hybrid structures are one of the leading platforms in the search for topological superconductivity. In these heterostructures, s-wave superconductivity combined with the strong spin-orbit coupling (SO) is expected to facilitate p-wave pairing. Direct probing of the symmetry of the order parameter is a daunting task, but presence of the SO in bulk non-centrosymmetric superconductors is expected to modify transport properties and add a linear in current and field correction to the critical current. In this work we report experimental investigation of critical currents in nanowires fabricated from InAs/Al heterostructures. We observe a highly non-monotonic dependence of the correction to the critical current on magnetic field, which is found to be linear at small fields (B<100mT), decreases to zero and switches sign at 200 mT, and vanishes above 300mT, all within the range of fields when the magnitude of the critical current changes only by a few percent. We also find that this dependence is not affected by a variation in wire length or crystallographic orientation but does depend on the relative orientation of the field and the current.