Theory of tunneling spectroscopy for chiral topological superconductors

TL;DR

This paper analyzes charge conductance at interfaces with chiral topological superconductors, revealing an even-odd effect related to the Chern number and Majorana edge modes, with implications for tunneling spectroscopy.

Contribution

It provides a theoretical framework for understanding tunneling conductance in chiral topological superconductors, highlighting the even-odd effect and Majorana mode interference.

Findings

Conductance vanishes for Chern number 0 or 2 at edge mode energies.

Universal conductance of 2e^2/h for Chern number 1.

Zero conductance in N=2 phase due to Majorana mode interference.

Abstract

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(ky, eV) with the momentum ky parallel to the interface and the 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 = Eedge(ky), the angle resolved conductance gamma(ky,Eedge(ky)) shows a pronounced even-odd effect; the conductance vanishes for N = 0 or 2 while it takes a universal value 2e^2/h for N = 1. In particular, in N = 2 phase, we find that the conductance gamma(ky,Eedge(ky)) becomes zero due to interference of two degenerate Majorana edge modes, although the corresponding surface spectral weight remains non-zero.