Surface terminations and layer-resolved tunneling spectroscopy of the 122 iron pnictide superconductors

Ang Li, Jia Xin Yin, Jihui Wang, Zheng Wu, Jihua Ma, Athena S. Sefat, Brian C. Sales, David G. Mandrus, Michael A. McGuire, Rongying Jin, Chenglin Zhang, Pengcheng Dai, Bing Lv, Ching Wu Chu, Xuejin Liang, P. H. Hor, C. S. Ting, Shuheng H. Pan

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


The surface terminations of 122-type alkaline earth metal iron pnictides AEFe2As2(AE=Ca,Ba) are investigated with scanning tunneling microscopy/spectroscopy. Cleaving these crystals at a cryogenic temperature yields a large majority of terminations with an atomically resolved (√2 × √2)R45 or 1 × 2 lattice, as well as a very rare termination of 1 × 1 lattice symmetry. By analyzing the lattice registration and selective chemical marking, we identify these terminations as (√2 × √2)R45-reconstructed AE, 1 × 2-reconstructed As, and (√2 × √2)R45-reconstructed Fe surface layers, respectively. Layer-resolved tunneling spectroscopy on these terminating surfaces reveals a well-defined superconducting energy gap on the As terminations, while the gap features become weaker on the AE terminations and absent on the Fe terminations. The superconducting gap is hardly affected locally by the As or AE surface reconstructions. The definitive identification of the surface terminations and the associated spectroscopic signatures shed light on the essential roles of As and the pnictogen-iron-pnictogen trilayer building block in iron-based superconductivity.

Original languageEnglish
Article number134520
JournalPhysical Review B
Issue number13
Publication statusPublished - 2019 Apr 30

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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