Superconductivity

Superconductivity is a phenomenon in which certain materials lose all resistance to electrical current when cooled below a certain temperature. This temperature is known as the critical temperature or Tc. In superconductors, electrical current flows with zero resistance and also expels any external magnetic field through Meissner effect

Meissner's effect

Meissner's effect is a phenomenon in which a superconductor expels any external magnetic field when cooled below its critical temperature. This effect can be observed as a perfect diamagnetism of a superconductor.

The Meissner effect is a direct consequence of the fact that a superconductor has zero electrical resistance. When an external magnetic field is applied to a superconductor, it generates circulating electric currents on its surface that create an opposing magnetic field, effectively cancelling out the applied field.

Type 1 Superconductors

Type 1 superconductors, also known as BCS superconductors, are characterized by a single critical temperature below which they become superconducting. These superconductors have a weak coupling between electrons and vibrations in the lattice and follow BCS theory of superconductivity. Examples of Type 1 superconductors include Aluminum, Lead, and Mercury.

Type 2 Superconductors

Type 2 superconductors, also known as intermediate-coupling superconductors, have a range of critical temperatures below which they become superconducting. These superconductors have a stronger coupling between electrons and vibrations in the lattice and do not follow BCS theory of superconductivity. Examples of Type 2 superconductors include Niobium-based, Yttrium-based and cuprate based superconductors.

BCS theory

The BCS (Bardeen-Cooper-Schrieffer) theory of superconductivity is a theoretical model that explains the mechanism of superconductivity in Type 1 superconductors.

The BCS theory describes the formation of these Cooper pairs through an attractive interaction between electrons, which is mediated by the vibrations of the crystal lattice. These vibrations, called phonons, provide the necessary energy for the electrons to form pairs. The pairs are then able to move through the material without resistance due to the absence of a net electrical charge. The BCS theory also explains the phenomenon of the energy gap in superconductors, which is the energy required to break a Cooper pair. It also predicts the temperature dependence of the critical magnetic field, which is the field required to break the Cooper pairs and suppress superconductivity. The BCS theory has been successful in explaining the properties of many conventional superconductors and continues to be an important framework for understanding superconductivity.

High Temperature Superconductors

High temperature superconductors (HTSCs) are materials that exhibit superconductivity at temperatures higher than the boiling point of liquid nitrogen (77K). These materials have been a subject of intense research since their discovery in 1986, as they have the potential to revolutionize many fields such as energy transmission and medical imaging. HTSCs are different from conventional superconductors in their mechanism of superconductivity and their crystal structure. The mechanism of superconductivity in HTSCs is not well understood, but it is believed to involve the formation of Cooper pairs in a different way than in conventional superconductors. HTSCs also have a more complex crystal structure, often involving copper-oxide layers.

Applications of superconductivity

Superconductivity has a wide range of potential applications, from energy transmission and storage to medical imaging and quantum computing. One of the most promising applications is in the field of energy transmission, where superconducting cables can transmit electricity with no loss of energy. Superconducting magnets are also used in MRI machines, particle accelerators, and fusion energy research. Another area of research is in the development of superconducting qubits for quantum computing. As the technology and understanding of superconductivity continues to advance, new and exciting applications are expected to emerge.