The Race Begins

When some conductors are cooled to very low temperatures their electrical resistance suddenly drops to zero—a current flows indefinitely through the material with nothing to stop it. In 1911, mercury was the first such “superconducting” material to be discovered, with a transition temperature of 4.1 K—below this temperature the material superconducts, above this temperature the material behaves like a regular conductor with resistance. Scientist have been searching for higher temperature superconductors ever since.

In 1986, Johannes Bednorz and Karl Müller demonstrated superconductivity in a copper-oxide compound at a temperature of 35 K, 12 K above the then previous record, starting an immediate race to find compounds with even higher transition temperatures. Their results were published in Zeitschrift für Physik B. In the two years that followed the duo’s discovery, superconducting transition temperatures of around 40 K, 90 K, and then 120 K were achieved in other copper-oxide compounds known as cuprates. Maw-Kuen Wu and his colleagues were the first to attain a transition temperature higher than the 77 K boiling point of liquid nitrogen, making superconductors more attractive for technological applications. Today the record temperature for superconductivity in a cuprate is around 140 K.

Summary from Physical Review Letters’ Milestone Collection