Tunneling Physics

I should like to discuss what I feel to be the two fundamental principles in our understanding of solid state physics to date. I think those of you who are experts on the subject will agree when I say that probably the outstanding features of solid state physics, as opposed to other branches of physics, are (1) that we deal with systems having a periodic structure of atoms or molecules of some sort - a crystal lattice, which is nearly perfect or nearly periodic over a large number of lattice spacings, and (2) that we deal with systems where the wave nature of the electron is of primary importance. I should like to put these two ideas together by considering what would happen, on a one-dimensional model, if we try to propagate an electron wave down through a periodic structure or lattice.