  A two-dimensional time-reversal symmetric topological superconductor is a
fully gapped system possessing a helical Majorana mode on the edges. This
helical Majorana edge mode (HMEM), which is a Kramer's pair of two chiral
Majorana edge modes in the opposite propagating directions, is robust under
time-reversal symmetry protection. We propose a feasible setup and accessible
measurement to provide the preliminary step of the HMEM realization by studying
superconducting antiferromagnetic quantum spin Hall insulators. Since this
antiferromagnetic topological insulator hosts a helical electron edge mode and
preserves effective time-reversal symmetry, which is the combination of
time-reversal symmetry and crystalline symmetry, the proximity effect of the
conventional s-wave superconducting pairing can directly induce a single HMEM.
We further show the HMEM leads to the observation of an $e^2/h$ conductance,
and this quantized conductance survives even in the presence of small
symmetry-breaking disorders.
