Crystal structures of Copper‐Based High‐T_c Superconductors

Abstract

Many copper‐oxide‐based superconducting compounds have been synthesized in recent years–currently more than 30 families are known, with superconducting transition temperatures up to 133 K. The structures of the various families are described, including La2CuO4, YBa2Cu3O7, single‐layer superconductors, double‐layer superconductors, and infinite layer materials (e.g., CaCuO2, as in the Figure).

Atomic Stripe Formation in Infinite-Layer Cuprates

“…For every Cu–O bond length between 1.850 and 2.000 Å, there exist a chemistry (typically called charge reservoir layer) that induces superconductivity, and this superconductivity appears throughout the phase diagram except for two distinct points at 1.950 and 1.895 Å, quantum critical points (QCPs) I and II, respectively. Copper–oxygen bond length values have been taken from refs − and for CaCuO 2 , Sr 1– x La x CuO 2 , R 2 CuO 4 , La 2– x Sr x CuO 4 , and Bi 2 Sr 2 CaCu 2 O 8+δ are from our experiments. Cuprate superconductors containing copper in a square-planar coordination environment have vacant apical sites and such cuprates are therefore not susceptible to Jahn–Teller distortions (JT free in zone I).…”

Sol–gel synthesis, structural and superconducting properties of (Hg1−ySey)Sr2(Y1−xCax)Cu2O6+δ

“…They are isostructural with a high-T c superconductor TlBa 2 CaCu 2 O 6+d (Tl/Ba-1212) [2], thus containing the CuO 2 layers that seem to be crucial for high-temperature superconductivity [3][4]. No diamagnetic transitions down to 12 K were detected for these phases even after oxygen treatments.…”