I came across this and said "Whoa! A major deja vu moment!"
This is a very nice paper on the principle of tunneling, and its use in tunneling spectroscopy that gives us quite a bit of information on the properties of a conventional superconductor. It describes an experiment for an undergraduate laboratory exercise. I had a deja vu moment because my PhD research was in tunneling spectroscopy using such point-contact method, but done on high-Tc superconductors which, at that time, was a "hot" commodity. I think we were one of the first groups that got a very clear V-shaped gap structure that was consistent with the d-wave symmetry.
In any case, this is a good paper to read if you want to learn an experimental technique, and certainly a good introduction to what we can learn by using such tunneling phenomenon. Of course, if you want to learn quite a bit more, than you have to read the same text that I used when I was a struggling graduate student - Wolf's standard text "Principle of Electron Tunneling Spectroscopy", which I think is still the bible for electron tunneling studies in solids.
This is also a very good opportunity to emphasize, especially those who are outside physics, of another example where a quantum phenomenon (tunneling) that is so well-known, that we are using it to study other things, in this case, the properties of a superconductor. While many may think that these quantum phenomena are nothing more than some esoteric properties that have no bearing on reality, the truth is that we make use of many of them, often to understand the stuff that we use everyday!
BTW, these undergraduate labs are getting to be more and more advanced. We already have an undergraduate experiment that showed the particle nature of light with a which-way-type experiment.