ABSTRACT
This chapter shows that muon spin research (μSR) techniques can provide information on the superconducting state that goes well beyond the characterisation of internal field distributions and flux lattice morphology. In the early stages of such μSR studies a rather surprising universal scaling relationship was soon recognized. All of fermion systems have been loosely classified as "exotic" or "unconventional" superconductors on the basis of their short coherence lengths, long penetration depths, high upper critical fields and highly correlated electronic structures. It is interesting to note that the transition temperatures of the so-called "conventional" BCS superconductors, such as Nb, do not follow the same scaling relationship. μSR has been widely used in systematic studies of vortex lattice structures, particularly in the high temperature cuprate superconductors. A systematic study of the many known classes of superconducting compounds using μSR may well provide a firm experimental basis upon which a theoretical interpolation between BCS and BE condensation mechanisms can be developed.
