High-temperature superconductivity

Not to be confused with Room-temperature superconductor.
A sample of bismuth strontium calcium copper oxide (BSCCO), which is currently one of the most practical high-temperature superconductors. Notably, it does not contain rare-earths. BSCCO is a cuprate superconductor based on bismuth and strontium. Thanks to its higher operating temperature, cuprates are now becoming competitors for more ordinary niobium-based superconductors, as well as magnesium diboride superconductors.

High-temperature superconductivity (high-Tc or HTS) is superconductivity in materials with a critical temperature (the temperature below which the material behaves as a superconductor) above 77 K (−196.2 °C; −321.1 °F), the boiling point of liquid nitrogen.[1] They are only "high-temperature" relative to previously known superconductors, which function at colder temperatures, close to absolute zero. The "high temperatures" are still far below ambient (room temperature), and therefore require cooling. The first breakthrough of high-temperature superconductor was discovered in 1986 by IBM researchers Georg Bednorz and K. Alex Müller.[2][3] Although the critical temperature is around 35.1 K (−238.1 °C; −396.5 °F), this new type of superconductor was readily modified by Ching-Wu Chu to make the first high-temperature superconductor with critical temperature 93 K (−180.2 °C; −292.3 °F).[4] Bednorz and Müller were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials".[5] Most high-Tc materials are type-II superconductors.

The major advantage of high-temperature superconductors is that they can be cooled using liquid nitrogen,[2] in contrast to the previously known superconductors that require expensive and hard-to-handle coolants, primarily liquid helium. A second advantage of high-Tc materials is they retain their superconductivity in higher magnetic fields than previous materials. This is important when constructing superconducting magnets, a primary application of high-Tc materials.

The majority of high-temperature superconductors are ceramic materials, rather than the previously known metallic materials. Ceramic superconductors are suitable for some practical uses but they still have many manufacturing issues. For example, most ceramics are brittle, which makes the fabrication of wires from them very problematic.[6] However, overcoming these drawbacks is the subject of considerable research, and progress is ongoing.[7]

The main class of high-temperature superconductors is copper oxides combined with other metals, especially the rare-earth barium copper oxides (REBCOs) such as yttrium barium copper oxide (YBCO). The second class of high-temperature superconductors in the practical classification is the iron-based compounds.[8][9] Magnesium diboride is sometimes included in high-temperature superconductors: It is relatively simple to manufacture, but it superconducts only below 39 K (−234.2 °C), which makes it unsuitable for liquid nitrogen cooling.

  1. ^ Timmer, John (May 2011). "25 years on, the search for higher-temp superconductors continues". Ars Technica. Archived from the original on 4 March 2012. Retrieved 2 March 2012.
  2. ^ a b Saunders, P. J.; Ford, G. A. (2005). The Rise of the Superconductors. Boca Raton, FL: CRC Press. ISBN 0-7484-0772-3.
  3. ^ Bednorz, J. G.; Müller, K. A. (1986). "Possible high Tc superconductivity in the Ba-La-Cu-O system". Zeitschrift für Physik B. 64 (2): 189–193. Bibcode:1986ZPhyB..64..189B. doi:10.1007/BF01303701. S2CID 118314311.
  4. ^ Wu, M. K.; Ashburn, J. R.; Torng, C. J.; Hor, P. H.; Meng, R. L.; Gao, L; Huang, Z. J.; Wang, Y. Q.; Chu, C. W. (1987). "Superconductivity at 93 K in a New Mixed-Phase Y–Ba–Cu–O Compound System at Ambient Pressure". Physical Review Letters. 58 (9): 908–910. Bibcode:1987PhRvL..58..908W. doi:10.1103/PhysRevLett.58.908. PMID 10035069.
  5. ^ "1987: J. Georg Bednorz, K. Alex Müller". Nobelprize.org. The Nobel Prize in Physics. Archived from the original on 19 September 2008. Retrieved 19 April 2012.
  6. ^ Plakida, N. (2010). High Temperature Cuprate Superconductors. Springer Series in Solid-State Sciences. Springer. p. 480. ISBN 978-3-642-12632-1.
  7. ^ "HTS Magnet Program". Brookhaven National Laboratory.
  8. ^ Choi, Charles Q. "A New Iron Age: New class of superconductor may help pin down mysterious physics". Scientific American. Retrieved 25 October 2019.
  9. ^ Ren, Zhi-An; Che, Guang-Can; Dong, Xiao-Li; Yang, Jie; Lu, Wei; Yi, Wei; et al. (2008). "Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO1−δ (Re=rare-earth metal) without fluorine doping". EPL. 83 (1): 17002. arXiv:0804.2582. Bibcode:2008EL.....8317002R. doi:10.1209/0295-5075/83/17002. S2CID 96240327.