Orbital selectivity of layer resolved tunneling on iron superconductor Ba0.6K0.4Fe2As2

TL;DR

This study uses STM/S to reveal layer-dependent orbital selectivity in tunneling spectra of Ba0.6K0.4Fe2As2, showing that different surface terminations probe distinct Fe-3d orbitals, advancing understanding of orbital-specific superconductivity.

Contribution

It demonstrates that layer-resolved tunneling in iron pnictide superconductors exhibits orbital selectivity, a novel insight into the real-space orbital nature of Cooper pairing.

Findings

Layer-dependent tunneling spectra show orbital selectivity.

Different surface terminations probe distinct Fe-3d orbitals.

Supports the concept of orbital-specific tunneling in multi-orbital materials.

Abstract

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.