Editing Superconductivity (section)

=== Critical temperature ===
A superconductor is generally considered ''[[High-temperature superconductivity|high-temperature]]'' if it reaches a superconducting state above a temperature of 30&nbsp;K (−243.15&nbsp;°C);<ref>{{Cite journal |last=Grant |first=Paul Michael |date=2011 |title=The great quantum conundrum |journal=Nature |publisher=Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved. |volume=476 |issue=7358 |pages=37–39 |doi=10.1038/476037a |pmid=21814269 |s2cid=27665903}}</ref> as in the initial discovery by [[Georg Bednorz]] and [[K. Alex Müller]].<ref name="Bednorz2" /> It may also reference materials that transition to superconductivity when cooled using [[liquid nitrogen]] – that is, at only ''T''<sub>c</sub>&nbsp;>&nbsp;77&nbsp;K, although this is generally used only to emphasize that liquid nitrogen coolant is sufficient. Low temperature superconductors refer to materials with a critical temperature below 30&nbsp;K, and are cooled mainly by [[liquid helium]] (''T''<sub>c</sub>&nbsp;>&nbsp;4.2&nbsp;K). One exception to this rule is the [[Iron-based superconductor|iron pnictide]] group of superconductors that display behaviour and properties typical of high-temperature superconductors, yet some of the group have critical temperatures below 30&nbsp;K.