We use scanning tunneling microscopy/spectroscopy (STM/S) to elucidate the Cooper pairing of the iron pnictide superconductor Ba0.6K0.4Fe2As2. By a cold-cleaving technique, we obtain atomically resolved termination surfaces with different layer identities. Remarkably, we observe that the low-energy tunneling spectrum related to superconductivity has an unprecedented dependence on the layer-identity. By cross-referencing with the angle-revolved photoemission results and the tunneling data of LiFeAs, we find that tunneling on each termination surface probes superconductivity through selecting distinct Fe-3d orbitals. These findings imply the real-space orbital features of the Cooper pairing in the iron pnictide superconductors, and propose a new and general concept that, for complex multi-orbital material, tunneling on different terminating layers can feature orbital selectivity.
@article{arxiv.1602.04949,
title = {Orbital selectivity of layer resolved tunneling on iron superconductor Ba0.6K0.4Fe2As2},
author = {J. -X. Yin and X. -X. Wu and Jian Li and Zheng Wu and J. -H. Wang and C. -S. Ting and P. -H. Hor and X. J. Liang and C. L. Zhang and P. C. Dai and X. C. Wang and C. Q. Jin and G. F. Chen and J. P. Hu and Z. -Q. Wang and Ang Li and H. Ding and S. H. Pan},
journal= {arXiv preprint arXiv:1602.04949},
year = {2020}
}