ABSTRACT
This chapter helps the reader to learn about the basic equations and physical concepts which explain low temperature superconductivity. The most convincing evidence that superconductors have zero resistivity is the observation of a persistent current. However, in a superconductor the screening currents flow without resistance and there is no dissipation. Furthermore, the Meissner effect in a superconductor is reversible. In its perfectly diamagnetic flux expelling superconducting state, electric currents cannot flow through the body of the material. The chapter is devoted to understanding the normal to superconducting phase transition region and the specific heat jump in superconductors. The key to explaining the occurrence of Type I or Type II superconductivity lies in examining how the free energy varies at the surface between the normal and the superconducting state. Bolometers are used in many astrophysics and astroparticle physics experiments. Experiments conducted in search of dark matter in the universe make use of thermometers made of superconducting materials.
