A type of superconductivity in which the critical temperature is much higher than ordinary superconductors. Among the high-temperature superconductors are metal oxide ceramics and synthetic organic conductors. Certain oxides of copper with barium and ytterbium have critical temperatures of about 100 K. The mechanism of high-temperature superconductivity is almost certainly different from ordinary superconductivity but is not known yet in spite of a great deal of theoretical and experimental effort since the phenomenon was discovered in 1986.