Which material earned Johannes Georg Bednorz and K. Alex Müller the 1987 Nobel Prize in Physics for discovering high-temperature superconductivity?

Barium lanthanum copper oxide earned Johannes Georg Bednorz and K. Alex Müller the 1987 Nobel Prize in Physics for discovering high-temperature superconductivity.

The material was a lanthanum barium copper oxide ceramic, commonly represented as La₂₋ₓBaₓCuO₄. Bednorz and Müller found that it became superconducting at temperatures far higher than those known for earlier superconductors. Their result, reported in 1986, triggered an intense worldwide search for related copper-oxide materials.

A superconductor carries electrical current with no electrical resistance below a critical temperature and can expel magnetic fields through the Meissner effect. “High-temperature” is relative: these materials still require cooling, usually with liquid nitrogen or other cryogenic systems. They are not superconducting at ordinary room temperature.

The discovery was especially surprising because the compound was a ceramic, whereas many earlier superconductors were metallic alloys. Later cuprate materials achieved substantially higher transition temperatures, but Bednorz and Müller’s discovery opened the modern high-temperature-superconductivity field.