Atomic origin of the coexistence of high critical current density and high Tc in CuBa2Ca3Cu4O10+δ superconductors
Xuefeng Zhang, Jianfa Zhao, Huijuan Zhao, Luchuan Shi, Sihao Deng, Jie Chen, Lunhua He, Zhiwei Hu, Changqing Jin, Jing Zhu
Abstract
Abstract For cuprate superconductors, a high critical transition temperature ( T c ) can be realized in compounds containing multiple CuO 2 layers in the unit cell, while a high critical current density ( J c ) is rarely sustained above liquid nitrogen temperature. The CuBa 2 Ca 3 Cu 4 O 10+δ (Cu-1234) superconductors synthesized under high oxygen pressure incredibly exhibit high T c (~117 K) and high J c (>10 4 A/cm 2 , 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 J c . Furthermore, metallic charge-reservoir blocks [Ba 2 CuO 3+δ ] were composed of unique compressed [CuO 6 ] octahedra, which induced many holes with 2 p z symmetry that significantly decreased the superconducting anisotropy and dramatically enhanced the interlayer coupling that guaranteed a high J c . On the other hand, optimally doped CuO 2 planes inside the thick superconducting blocks [Ca 3 Cu 4 O 8 ] maintained a high T c . Our results are applicable to design and synthesis of new superconductors with “double high” traits.