TABLE OF CONTENTS In 1911, Dutch physicist H. K. Onnes discovered superconductivity in mercury at a temperature of 4 K soon after he liquefied helium for the first time. Onnes was awarded the Nobel Prize in Physics for his work on the properties of matter at low temperatures in 1913. Later, Fritz London developed a phenomenological theory of superconductivity in 1934 with his brother Heinz. The basic idea is that the electrons in a superconductor condense into a superfluid state characterized by a single rigid wavefunction ?( r) = ?( r) e i? ( r ) also known as the order parameter. In 1950 Ginzburg and Landau generalized the London theory by introducing a complex, temperature-dependent order parameter. John Bardeen, Leon Cooper, and J. Robert Schrieffer reported the first microscopic theory of superconductivity in 1957 known as the BCS theory.
The superconducting state is characterized by (1) zero electrical resistance to current below a material dependent transition temperature T c, (2) the expulsion of magnetic flux from the bulk of the superconductor, and (3) flux quantization. Superconductivity is now known to be a remarkable example of quantum effects acting on a macroscopic scale. Certain metals, including mercury, lead, tin, and more recently discovered copper oxide ceramics, undergo a superconducting phase transition below T c. Electron spins become oppositely paired resulting in the formation of a spin-zero quasi particle, or Cooper pair, that may pass through the material unimpeded.
Electrons in a superconductor...
