1. Reminders

1.1 Superconducting state

The superconducting state – previously described by J. Lesueur [E 1 110] – occurs in certain classes of materials (for example, many metals and certain perovskite-type ceramics, etc.) when the temperature falls below a so-called critical temperature. Superconductivity is primarily characterized by a strictly zero resistance to direct current and by the Meissner effect, which is the expulsion of a magnetic field from the core of a superconducting material. In the...