Relations between normal state nonreciprocal transport and the superconducting diode effect in the trivial and topological phases

Nonreciprocal transport effects can occur in the normal state of conductors and in superconductors when both inversion and time-reversal symmetry are broken. Here, we consider systems where magnetochiral anisotropy of the energy spectrum due to an externally applied magnetic field results in a rectification effect in the normal state and a superconducting (SC) diode effect when the system is proximitized by a superconductor. Focusing on nanowire systems, we obtain analytic expressions for both normal state rectification and SC diode effects that reveal the commonalities—as well as differences—between these two phenomena. Furthermore, we consider the nanowire brought into an (almost) helical state in the normal phase or a topological SC phase when proximitized. In both cases, this reveals that the topology of the system considerably modifies its nonreciprocal transport properties. Our results provide insights into how to determine the origin of nonreciprocal effects and further evince the strong connection of nonreciprocal transport with the topological properties of a system.