Superconductivity was one of the most studied topics in the
last 20 years, thanks to the discovery of high-temperature
superconductors (HTSs). Exotic features of superconductivity
are direct consequence of quantum-mechanical phenomena.
Quantum-mechanical phenomena are applicable to nanoscopic
world. However, superconductivity is' an exception to
this because it is a collective state of quantum-mechanical
entities (i.e., charge carriers, such as electrons) that extends
through whole of the superconductor on a macroscopic scale.
Thanks to this, quantum-mechanical phenomena associated
with superconductivity can be observed and used in our
macroscopic world. Most common examples of this are transport
of electrical current with no resistance and levitation.
Such phenomena can be compared to the motion of electrons
around atomic nuclei without loss of energy through radiation,
which can only be described by quantum mechanics.
Superconductors offer experience of such phenomena in our
everyday world, with a possibility of practical applications of
these phenomena in our macroscopic world.