Cuprate

Cuprate refers to compounds containing copper and oxygen. In chemistry, the term covers copper oxides such as copper(I) oxide and copper(II) oxide, but in condensed matter physics it is most often used for copper oxide–based materials that host copper oxide planes. The cuprates include a broad family of layered transition metal oxides whose chemistry is dominated by CuO2 planes.

The crystal structure of most cuprates is highly layered: copper-oxide planes separated by spacer layers that donate or remove charge. In CuO2 planes, copper assumes a square-planar or square-pyramidal coordination with oxygen. The parent compounds are typically Mott insulators with antiferromagnetic order, and superconductivity appears when charge carriers are introduced by chemical substitution or oxygen content adjustment.

Doping cuprates by introducing holes (or electrons) into CuO2 planes leads to superconductivity in many families, with transition temperatures, Tc, that can exceed the boiling point of liquid nitrogen. Notable families include La2−xSrxCuO4, YBa2Cu3O7−δ, and Bi2Sr2CaCu2O8+x. The superconducting state in cuprates is widely believed to involve unconventional pairing with predominantly d-wave symmetry, and the normal state shows unconventional, strongly correlated behavior including a pseudogap phase.

Synthesis and preparation typically involve high-temperature solid-state routes and careful control of oxygen content, annealing in oxygen, and cation substitutions. Potential applications include high-field magnets, power cables, and electronic devices, although practical use is constrained by cooling requirements and material brittleness.

See also: cuprate superconductors, copper oxide, high-temperature superconductivity.