Study of Superconductivity

In this chapter we first introduce the basic concept of superconductivity and its characteristic parameters (magnetic penetration depth, coherence length, superconducting gap, and symmetry), which are necessary to understand a \(\mu \) SR experiment in a superconductor. What kind of microscopic and macroscopic information and how \(\mu \) Sr is used to extract it from a type-II superconductor in the vortex state is discussed. Different types of analysis of the \(\mu \) SR asymmetry spectra and of the magnetic field distribution are discussed and typical examples are given. The use of \(\mu \) SR to search for spontaneous magnetic fields in superconductors as a signature of time-reversal symmetry breaking and to study the interplay of magnetism/superconductivity in unconventional superconductors is illustrated with examples. Finally, an experiment to study the intermediate state of a type-I superconductor is discussed.