1911
The Dutch physicist Kamerlingh Onnes discovers superconductivity in mercury during experiments with the liquefaction of helium. The disappearance of electrical resistance was only observed at an extremely low transition temperature of 4.2 kelvin (minus 268 degrees Celsius). The transition temperature, also known as the critical temperature, is the temperature at which the transition from the normal conducting to the superconducting phase takes place.
1957
Three US physicists develop the BCS theory to explain superconductivity in metals.
1983
Georg Bednorz and Karl Alexander Müller begin their research into ceramics made from copper oxides. At the time, these materials were only known as semiconductors or insulators. Prior to their experiments, it was niobium-germanium, an alloy of germanium and niobium, that had the highest known transition temperature of 23.5 kelvin (minus 249 degrees Celsius).
1986
Bednorz and Müller demonstrate a transition temperature of 35 kelvin (minus 238 degrees Celsius) in a barium-lanthanum cuprate and so discover the class of ceramic superconductors. From then on, materials with a significantly higher transition temperature than traditional superconductors are referred to as high-temperature superconductors.
2008
Japanese researchers discover a new class of high-temperature superconductors: compounds of iron, lanthanum, phosphorus and oxygen can have superconducting properties. With admixtures such as arsenic, the transition temperature rises to up to 56 kelvin (minus 217 degrees Celsius).
2019
Belarusian physicist Mikhail Eremets breaks the previous temperature record at the Max Planck Institute for Chemistry in Mainz. From ten parts hydrogen and one part lanthanum, he creates lanthanum hydride, which is superconducting at minus 23 degrees Celsius – but only at 17,000 times atmospheric pressure.
