  The critical current of a superconductor can depend on the direction of
current flow due to magnetochiral anisotropy when both inversion and
time-reversal symmetry are broken, an effect known as the superconducting (SC)
diode effect. Here, we consider one-dimensional (1D) systems in which
superconductivity is induced via the proximity effect. In both topological
insulator and Rashba nanowires, the SC diode effect due to a magnetic field
applied along the spin-polarization axis and perpendicular to the nanowire
provides a measure of inversion symmetry breaking in the presence of a
superconductor. Furthermore, a strong dependence of the SC diode effect on an
additional component of magnetic field applied parallel to the nanowire as well
as on the position of the chemical potential can be used to detect that a
device is in the region of parameter space where the phase transition to
topological superconductivity is expected to arise.
