The Josephson Effect

Superconductivity was discovered as early as 1911,¹ but it was a long time before the modern concept of the superconducting state of matter was established. The main milestones along the way were the discovery of the Meissner effect,² the formulation of phenomenological theories by Londons^3,4 and by Ginzburg and Landau,⁵ and, eventually, the creation of the microscopic theory by Bardeen, Cooper, and Schrieffer⁶ (BCS), with later important contributions by Bogolyubov and Gor’kov⁷. Nevertheless, the theoretical prediction^4–8,P.1 and experimental observation^9,10,P.2 of the coherent (or “macroscopic quantum”) phenomena in superconductors have proved to be necessary for the final formulation of the concept. According to this concept, a macroscopic coherence of the current carriers in superconductors—the Cooper pairs of electrons—is the basis of all unusual properties of superconductors observed. We will discuss this point in somewhat more detail (see also References P.29-P.41).