cupratescopper

Cuprates are a family of copper oxide compounds that are among the most studied high-temperature superconductors. They are layered materials built from copper-oxygen planes, separated by charge-reservoir layers that regulate the number of charge carriers in the planes. The essential chemical motif is copper in oxide coordination within CuO2 sheets.

In most cuprates copper is in the +2 oxidation state within the CuO2 planes. Doping, achieved by substituting ions in the lattice or by varying oxygen content, changes the carrier concentration and drives the material from an insulating to a metallic and then a superconducting state. The typical structural feature is CuO2 planes stacked with various spacer layers, producing highly anisotropic electronic behavior.

Electronicly, the parent members of cuprates are antiferromagnetic Mott insulators. Introducing holes through doping suppresses antiferromagnetism and gives rise to a superconducting phase at low temperatures. The superconducting state in cuprates is unconventional, with a predominantly d-wave symmetry of the order parameter. The resulting phase diagram includes antiferromagnetism, superconductivity, and a pseudogap region, whose nature remains a central topic of study.

Notable families include La2−xSrxCuO4, YBa2Cu3O7−δ, Bi2Sr2CaCu2O8+δ, and Nd2−xCexCuO4. Cuprates exhibit critical temperatures well above those of conventional superconductors, with many compounds superconducting above 90 K and some reaching about 130 K at ambient pressure.

Historically, cuprates were discovered in 1986 by Bednorz and Müller, a breakthrough that launched the field of high-temperature superconductivity and earned them the Nobel Prize in Physics in 1987. Practical use faces challenges such as ceramic brittleness, sensitivity to oxygen content, and the need for cryogenic cooling, but research continues to explore applications in magnets and potential power transmission.