Atomic origin of the coexistence of high critical current density and high Tc in CuBa2Ca3Cu4O10+δ superconductors

Abstract

For cuprate superconductors, a high critical transition temperature (Tc) can be realized in compounds containing multiple CuO2 layers in the unit cell, while a high critical current density (Jc) is rarely sustained above liquid nitrogen temperature. The CuBa2Ca3Cu4O10+δ (Cu-1234) superconductors synthesized under high oxygen pressure incredibly exhibit high Tc (~117 K) and high Jc (>104 A/cm2, 100 K) values. Here, the “double high” traits of Cu-1234 were investigated with advanced scanning transmission electron microscopy. It was revealed that ordering vacancies and plate-like 90° microdomains induced efficient microstructure pinning centers that suppressed vortex flux flow and enhanced Jc. Furthermore, metallic charge-reservoir blocks [Ba2CuO3+δ] were composed of unique compressed [CuO6] octahedra, which induced many holes with 2pz symmetry that significantly decreased the superconducting anisotropy and dramatically enhanced the interlayer coupling that guaranteed a high Jc. On the other hand, optimally doped CuO2 planes inside the thick superconducting blocks [Ca3Cu4O8] maintained a high Tc. Our results are applicable to design and synthesis of new superconductors with “double high” traits.