Superconductivity

Abstract

In Chap. 9, the basic aspects of the phenomenon of electrical conductivity in metals were introduced and explained. The finite resistance of these materials originates from the fact that a real crystal always exhibits deviations from perfect lattice periodicity: phonons and defects. An infinitely high electrical conductivity is unthinkable in this description, because (1) a crystal without a certain degree of disorder is inconceivable according to the second law of thermodynamics, and (2) even in the absence of phonon and defect scattering, electron-electron scattering will still cause resistance (Sect. 9.3). However, in the year 1911, Onnes [10.1] discovered that the electrical resistance of mercury approaches an unmeasurably small value when it is cooled below 4.2 K.