1. For one-particle tunneling between normal metal and a superconductor,
show qualitatively how the coherence factors

and

drop out from the expression for the tunneling current.

For one particle tunneling, one has to create single particle excitations
in a superconductor. It involves electron state

as well as hole state

in such a way that the
coherence factors

and

drop out from
the expression for the tunneling current.

In the semiconductor model the superconducting gap is treated as the
band gap of the semiconductor. Howevere, one must remember that an
elementary excitation in a superconductor is a linear combination
of states above as well as below the superconducting gap.