Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China.
Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, Hefei, 230031, China.
Adv Mater. 2023 Jun;35(26):e2301021. doi: 10.1002/adma.202301021. Epub 2023 May 10.
Carbonates (CO ) have always been known as impurities to degrade the superconductivity in cuprate high-Tc superconductors. Herein, the atomic arrangement of carbonates is directly visualized in (Cu,C)Ba Ca Cu O via integrated differential phase contrast (iDPC) combined with state-of-the-art scanning transmission electron microscopy. The carbon atoms replace Cu atoms in the charge-reservoir layers, contributing to the formation of carbonates through strong orbital hybridization with the surrounding oxygen atoms. Using first-principles calculations, the spatial configuration of the carbonate groups is confirmed and their influence on the local crystal lattice and electronic states is further investigated. The carbonates not only accommodate distortions by improving the flatness of the outer CuO layers but also reduce the density of states at the Fermi level. These two factors play competitive roles to affect the superconductivity. This study provides direct evidence of the presence of CO groups and gains an insight into the underlying mechanism of superconductivity in oxycarbonate superconductors.
碳酸根（CO ）一直被认为是降低铜酸盐高温超导材料超导性的杂质。在此，通过集成差分相衬（iDPC）结合最先进的扫描透射电子显微镜，直接观察到（Cu，C）Ba Ca Cu O 中的碳酸根原子排列。碳原子取代电荷储存层中的 Cu 原子，通过与周围氧原子的强轨道杂化，有助于形成碳酸根。利用第一性原理计算，进一步证实了碳酸盐基团的空间构型及其对局部晶格和电子态的影响。碳酸根不仅通过提高外层 CuO 层的平整度来容纳畸变，而且还降低费米能级处的态密度。这两个因素起着竞争的作用，影响超导性。本研究提供了 CO 基团存在的直接证据，并深入了解了氧碳酸盐超导体中超导性的潜在机制。
