Superconductivity

Superconductivity is a phenomenon occurring in certain materials at extremely low temperatures (“crogenic temperatures”), characterised by them exhibiting exactly zero electrical resistance. Superconductivity occurs in a wide variety of materials, including simple elements like tin and aluminium, various metallic alloys and some heavily-doped semiconductors. Superconductivity does not occur in noble metals like gold and silver, or in most ferromagnetic metals.

Cryogenic temperatures are usually expressed in the units of Kelvin (K) - this can be viewed as a measure of the number of degrees Celsius above Absolute Zero (-273.15°C).

Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes, who was studying the resistance of solid mercury at cryogenic temperatures using the recently-discovered liquid helium as a refrigerant. At the temperature of 4.2 K, he observed that the resistance abruptly disappeared. In subsequent decades, superconductivity was found in several other materials. In 1913, lead was found to superconduct at 7 K, and in 1941 niobium nitride was found to superconduct at 16 K.
In 1986 the discovery was made of a family of cuprate-perovskite ceramic materials now known as high-temperature superconductors (HTS), with critical temperatures in excess of 90 K. The discovery of HTS, by Bednorz and Mueller, was awarded the Nobel Prize in 1987

Superconducting magnets are some of the most powerful electromagnets known. They are used in MRI and NMR machines and the beam-steering magnets used in particle accelerators. They can also be used for magnetic separation, where weakly magnetic particles are extracted from a background of less or non-magnetic particles, as in the pigment industries.

Superconductors are used to build Josephson Junctions which are the building blocks of SQUIDs (superconducting quantum interference devices), the most sensitive magnetometers known. Series of Josephson devices are used in the definition of the SI Volt. Depending on the particular mode of operation, a Josephson Junction can be used as photon detector or as mixer. The large resistance change at the transition from the normal to the superconducting state is used to build thermometers in cryogenic micro-calorimeter photon detectors.
Other early markets are arising where the relative efficiency, size and weight advantages of devices based on HTS outweigh the additional costs involved.

Promising future applications include high-performance transformers, power storage devices, electric power transmission, electric motors (e.g. for vehicle propulsion, as in vactrains or maglev trains), magnetic levitation devices, and Fault Current Limiters. However superconductivity is sensitive to moving magnetic fields so applications that use alternating current (e.g. transformers) will be more difficult to develop than those that rely upon direct current.

Mesaplexx is applying and exploiting the phenomenon of high temperature superconductivity to manufacture commercial volumes of RF and Microwave devices, to enhance the performance of wireless communications systems.