Theory of tunneling spectroscopy in a superconducting topological insulator

•We show tunneling conductance for possible parings of superconducting CuxBi2Se3.•A zero-bias conductance peak can appear in this system.•This is because the surface-state transition in the momentum space.•The surface state transition stems from surface Dirac fermions in the normal state.

We calculate tunneling conductance of normal metal and superconducting topological insulator CuxBi2Se3 junctions for the possible pairing symmetries. In the presence of gapless Andreev bound states (ABSs), the tunneling conductance shows a zero-bias peak even for the three-dimensional full-gap superconducting state. This zero-bias conductance peak stems from the enhancement of the surface density of states induced by the surface-state transition in momentum space.