Scanning Tunneling Microscopy / Spectroscopy on Multi-Layered Cuprate Superconductor Ba2Ca5Cu6O12 (O1-x Fx)2

Sugimoto A.

Shohara K.

Ekino T.

Watanabe Y.

Harada Y.

Mikusu S.

Tokiwa K.

Watanabe T.

Physica C: Superconductivity

Scanning tunneling microscopy/spectroscopy (STM/STS) measurements on multi-layered cuprate superconductor Ba2Ca5Cu6O12 (O 1-x Fx)2 are carried out. STM topographies show randomly distributed bright spot structures with a typical spot size of ~ 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 Δ ~ 15 meV and ~ 90 meV, respectively. The small gap structure disappears at the temperature close to TC, while the large gap persists up to ~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 2ΔS /KBTC = 4.9 is obtained with TC = 70 K, which is determined from temperature dependence of the tunneling spectra.

Ba2Ca5Cu6O12 (O 1-xF x)2

F0256

STM

tunneling spectroscopy

Physics [ 420 ]

eng

Elsevier B.V.

Copyright (c) 2009. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。

[ISSN] 0921-4534

[NCID] AA11461984

[DOI] 10.1016/j.physc.2009.01.019

[DOI] https://doi.org/10.1016/j.physc.2009.01.019