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Ca₁₀(Pt₄As₈)(Fe₂As₂)₅ contains both superconducting building blocks (Fe₂As₂ layers) and conducting spacers (Pt₄As₈ layers), unlike insulating spacers in other Fe-based superconductors. Prior work showed the important role played by the charge environment and surface structures in its superconducting properties: evidence for superconductivity is absent in bare Pt₄As₈ surface but recovers when Ca atoms are atop [1]. Different surface reconstructions also lead different superconducting features. We use scanning tunneling microscopy and spectroscopy (STM/S) to directly confirm the role of charge balance and surface structures on superconductivity in this compound. Cleaving provides large areas of bare Pt₄As₈ layer, which originally does not show superconducting features. Depositing additional Ca atoms on the bare Pt₄As₈ surface, while the sample is on the STM scanning stage, results in changes in spectral features. We will discuss the relationship between surface structures and superconducting features based on the Ca structures formed by controlling the deposition temperature.
[1] J. Kim et al., Sci. Rep. 6, 35365 (2016).