Theory of tunneling spectroscopy for chiral topological superconductors

We study the charge conductance of an interface between a normal metal and a superconducting quantum anomalous Hall system, based on the recursive Green's function. The angle-resolved conductance gamma(k(y), eV) with momentum k(y) parallel to the interface and bias voltage V shows a rich structure depending on the Chern number N of the system. We find that when the bias voltage is tuned to the energy dispersion of the edge mode, eV = E-edge(k(y)), the angle-resolved conductance gamma(k(y), E-edge(k(y))) shows a pronounced even-odd effect; the conductance vanishes for N = 0 or 2, while it takes the universal value 2e(2)/h for N = 1. In particular, in the N = 2 phase, we find that the conductance gamma(k(y), E-edge(k(y))) becomes 0 due to the interference of two degenerate Majorana edge modes, although the corresponding surface spectral weight remains nonzero.