ABSTRACT
Although the concept of tunnelling was long known theoretically and was already being used by 1928 for the explanation of experimental data for, e.g., the natural decay of certain heavy nuclei by α -particle emission (Gamov 1928), electron tunnelling in solid-state structures was observed only quite late. In 1958 Esaki observed electron tunnelling in narrow semiconductor p-n junctions (Esaki 1958) and was awarded the Nobel prize in 1973. Also in 1973, Giaever was awarded the Nobel prize for his demonstration of single-electron tunnelling through a thin oxide barrier (<5 nm) between metal electrodes (Giaever 1960). In particular, electron tunnelling between superconducting electrodes turned out to be a very interesting tool for investigating the electronic structure of superconductors. Also the tunnelling of Cooper pairs through barriers seemed to be possible, but the probability of it occurring seemed to be so small compared with the probability for single-electron tunnelling that its contribution to the total tunnelling current could be neglected (see e.g. Tinkham 1985). Unimpressed by this pessimistic prediction, Josephson published a paper (Josephson 1962) in 1962 in which he predicted the possibility and consequences of Cooper pair tunnelling for which he was awarded the Nobel prize, also in 1973. Anderson (1970) gave a very interesting description of how Josephson discovered this effect.
