Superconductor
Introduction
Superconductivity is a quantum mechanical phenomenon where certain materials exhibit zero electrical resistance and expulsion of magnetic fields when cooled below a characteristic critical temperature. This state, first discovered in mercury by Heike Kamerlingh Onnes in 1911, has been observed in many physical systems, including complex organic molecules, high-temperature ceramics, and certain pure elements.
Discovery
The phenomenon of superconductivity was first discovered in mercury by Dutch physicist Heike Kamerlingh Onnes in 1911. When he cooled mercury to the temperature of liquid helium, 4 degrees Kelvin, he observed that the mercury's resistance suddenly disappeared. The zero resistance has been confirmed by many experiments since.
Theory
The theoretical understanding of superconductivity began with the development of the Bardeen–Cooper–Schrieffer (BCS) theory in 1957. The BCS theory explains superconductivity in conventional superconductors as a microscopic effect caused by a condensation of Cooper pairs into a boson-like state. The theory also provides a microscopic explanation for the Meissner effect, in which a superconductor expels all magnetic fields from its interior when it transitions into the superconducting state.
High-Temperature Superconductors
The discovery of high-temperature superconductors, materials that exhibit superconducting properties at temperatures much higher than those of conventional superconductors, was a major breakthrough in the field. These materials, first discovered in 1986, have critical temperatures above 77 K, the boiling point of liquid nitrogen, a commonly available coolant.
Applications
Superconductors have many potential applications. In power transmission, they can be used to create power lines that can carry large amounts of electrical current without loss. In magnetic resonance imaging (MRI), superconducting magnets are used to generate the strong magnetic fields necessary for imaging. Other potential applications include quantum computing, magnetic levitation trains, and particle accelerators.
Challenges and Future Research
Despite the potential of superconductors, there are still many challenges to their widespread use. These include the high cost of cooling, the difficulty of fabricating large quantities of high-temperature superconductors, and the need for more research to fully understand the properties of these materials. Future research in the field is likely to focus on finding new superconducting materials, understanding the mechanisms of high-temperature superconductivity, and developing practical applications.