high temperature superconductor

High-temperature superconductors (abbreviated high-Tc or HTS) are materials that behave as superconductors at unusually high temperatures. The first high-Tc superconductor was discovered in 1986 by IBM researchers Georg Bednorz and K. Alex Müller, who were awarded the 1987 Nobel Prize in Physics “for their important break-through in the discovery of superconductivity in ceramic materials”. Whereas “ordinary” or metallic superconductors usually have transition temperatures (temperatures below which they superconduct) below , HTS have been observed with transition temperatures as high as . Until 2008, only certain compounds of copper and oxygen (so-called “cuprates”) were believed to have HTS properties, and the term high-temperature superconductor was used interchangeably with cuprate superconductor for compounds such as bismuth strontium calcium copper oxide (BSCCO) and yttrium barium copper oxide (YBCO). However, several iron-based compounds (the iron pnictides) are now known to be superconducting at high temperatures. For an explanation about Tc (the critical temperature for superconductivity), see Superconductivity#Superconducting phase transition and the second bullet item of BCS theory#Successes of the BCS theory.