Scanning tunneling microscopy/spectroscopy on multi-layered cuprate superconductor Ba(2)Ca(5)Cu(6)O(12) (O(1-)(x)) F(x)))(2

• Published in: Physica. C, Superconductivity Vol. 469; no. 15-20; pp. 1020 - 1023
• Main Authors: Sugimoto, A, Shohara, K, Ekino, T, Watanabe, Y, Harada, Y, Mikusu, S, Tokiwa, K, Watanabe, T
• Format: Journal Article
• Language: English
• Published: 01.10.2009
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2009.01.019

Scanning tunneling microscopy/spectroscopy (STM/STS) measurements on multi-layered cuprate superconductor Ba(2)Ca(5)Cu(6)O(12) (O(1-)(x)) F(x)))(2) are carried out. STM topographies show randomly distributed bright spot structures with a typical spot size of [not, vert, similar]0.8 nm. These bright spots are occupied about 28% per one unit cell of c-plane, which is comparable to the regular amount of apical oxygen of 20% obtained from element analysis. Tunneling spectra simultaneously show both the small and the large gap structures. These gap sizes at 4.9 K are about [not, vert, similar]15 meV and [not, vert, similar]90 meV, respectively. The small gap structure disappears at the temperature close to T(C), while the large gap persists up to [not, vert, similar]200 K. Therefore, these features correspond to the superconducting gap and pseudogap, respectively. These facts give evidence for some ordered state with large energy scale even in the superconducting state. For the superconducting gap, the ratio of 2/K(B)T(C) = 4.9 is obtained with T(C) = 70 K, which is determined from temperature dependence of the tunneling spectra.