Cuprate superconductor
Interest in cuprates sharply increased in 1986 with the discovery of high-temperature superconductivity in the Non-stoichiometric cuprate lanthanum barium copper oxide La2−xBaxCuO4. The Tc for this material was 35 K, well above the previous record of 23K. Thousands of publications examine the superconductivity in cuprates between 1986 and 2001, and Bednorz and Müller were awarded the Nobel Prize in Physics only a year after their discovery.
From 1986 to 2008, many cuprate superconductors were identified. Most famous is yttrium barium copper oxide (YBa2Cu3O7, "YBCO" or "1-2-3"). Another example is bismuth strontium calcium copper oxide (BSCCO or Bi2Sr2CanCun+1O2n+6-d) with Tc = 95–107 K depending on the n value. Thallium barium calcium copper oxide (TBCCO, TlmBa2Can−1CunO2n+m+2+δ) was the next class of high-Tc cuprate superconductors with Tc = 127 K observed in Tl2Ba2Ca2Cu3O10 (TBCCO-2223) in 1988. The highest confirmed, ambient-pressure, Tc is 135 K, achieved in 1993 with the layered cuprate HgBa2Ca2Cu3O8+x. Few months later, another team measured superconductivity above 150K in the same compound under applied pressure (153 K at 150 kbar).
Cuprate superconductors usually feature copper oxides in both the oxidation state 3+ as well as 2+. For example, YBa2Cu3O7 is described as Y3+(Ba2+)2(Cu3+)(Cu2+)2(O2−)7. All superconducting cuprates are layered materials having a complex structure described as a superlattice of superconducting CuO2 layers separated by spacer layers where the misfit strain between different layers and dopants in the spacers induce a complex heterogeneity that in the superstripes scenario is intrinsic for high temperature superconductivity.
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