Ever since the discovery of high-Tc superconductivity in layered cuprates, the roles that individual layers play have been debated, due to difficulty in layer-by-layer characterization. While there is similar challenge in many Fe-based layered superconductors, the newly-discovered Ca10(Pt4As8)(Fe2As2)5 provides opportunities to explore superconductivity layer by layer, because it contains both superconducting building blocks (Fe2As2 layers) and intermediate Pt4As8 layers. Cleaving a single crystal under ultra-high vacuum results in multiple terminations: an ordered Pt4As8 layer, two reconstructed Ca layers on the top of a Pt4As8 layer, and disordered Ca layer on the top of Fe2As2 layer. The electronic properties of individual layers are studied using scanning tunneling microscopy/spectroscopy (STM/S), which reveals different spectra for each surface. Remarkably superconducting coherence peaks are seen only on the ordered Ca/Pt4As8 layer. Our results indicate that an ordered structure with proper charge balance is required in order to preserve superconductivity.
@article{arxiv.1607.08197,
title = {Interrogating the superconductor Ca10(Pt4As8)(Fe2-xPtxAs2)5 Layer-by-layer},
author = {Jisun Kim and Hyoungdo Nam and Guorong Li and A. B. Karki and Zhen Wang and Yimei Zhu and Chih-Kang Shih and Jiandi Zhang and Rongying Jin and E. W. Plummer},
journal= {arXiv preprint arXiv:1607.08197},
year = {2016}
}