Atomically-resolved interlayer charge ordering and its interplay with superconductivity in YBa₂Cu₃O_6.81

Joint seminar of Fritz Haber Institute and Institute for Molecular Science, Japan. Charge order (CO) has been recognized as one of the most important competing order in superconductive cuprates. In YBa₂Cu₃O_6+x (YBCO), CO could only be investigated by x-ray diffraction in under-doped YBCO with low critical temperatures (T_C), but not in highly-doped YBCO with high T_C suitable for device applications, due to the competing superconductive phase. Therefore, the most fundamental physical mechanisms governing CO, for example, the role of so-called charge reservoir (Cu-O chain) layers in CO and the spatial interplay of CO and SC, in highly-doped YBCO are still unclear. Here, we present the direct real-space cross-sectional scanning tunneling microscopy (XSTM) imaging with atomic resolution to characterize the atomically resolved electronic structure along the c [001] direction in high-temperature superconductive cuprates. We demonstrate that CO occurs on CuO plane and chain layers with an antiphase correlation along the c-axis direction governed by Coulomb repulsion rather than Josephson tunneling. Similarly, superconductive coherence is also observed in chain and plane layers. In addition, both phases exhibit a proximity-like boundary region mutually suppressing CO and SC. The present atomically-resolved XSTM provides a detailed insight into the unexplored interlayer coupling and its spatial interplay with superconductivity and therefore offers a new approach to unravel the fundamental physical mechanisms of superconductivity in cuprates.[1]Reference[1] Chun-Chih Hsu, Bo-Chao Huang, Michael Schnedler, Ming-Yu Lai, Yuh-Lin Wang, Rafal E. Dunin Borkowski, Chia-Seng Chang, Ting Kuo Lee, Philipp Ebert, and Ya-Ping Chiu, “Atomically-resolved interlayer charge ordering and its interplay with superconductivity inYBa₂Cu₃O_6.81”, Nature Communications, 12, 3893 (2021).