Superconductivity was discovered by Onnes about a century ago, and is still an important disciplinein physics. It not only promotes the development of physics, but also has extensive applications and improves the living standards of people. The superconductors have two basic properties: one is the zero resistance which means that a current can flow without dissipation; the other is the Meissner effect which says that superconductors can screen magnetic fields. Moreover, there are many other important phenomena related to superconductivity, such as Josephson effect, magnetic flux quantization, etc. Theories describing superconductivity contain the BCS theory, the Ginzburg-Landau (GL) theory, the London equations, and so on.
As we know that electrons have both charge and spin degrees of freedom. The properties of materials related to charge degree of freedom have been studied for a long time, while the properties related to spin are less studied. However, many useful properties related to the spin degree of freedom have been discovered in this decade, thus this field has drawn more attentions and has experienced a great development. Some effects related to spin, which can be seen as the analogues of effects related to charge, have been found. For instance, the quantum spin Hall effect (topological insulator) is the analogue of the quantum Hall effect.