2025/06/19 by Song, Sang Yong, Halász, Gábor B., Yan, Jiaqiang +2
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Iron-based superconductors research #Physics of Superconductivity and Magnetism #Rare-earth and actinide compounds #Superconductivity (cond-mat.supr-con)
paper · pdf · doi:10.48550/arxiv.2506.16384
openalex publication_date 2025/06/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We investigate the orbitally resolved superconducting properties of bulk FeSe using scanning tunneling microscopy (STM). We find that the spectral weights of both the large Δ1 and small Δ2 superconducting gaps remain nearly unchanged at the top Se sites as the STM tip approaches atomic contact. In contrast, the spectral weight of Δ2 increases significantly at the Fe and bottom Se sites. These results suggest that the gap Δ2 is localized in the xy-plane and likely associated with the dxy orbital band. Furthermore, we observe a long-range suppression of the large gap Δ1 near one-dimensional (1D) defects such as twin boundaries, wrinkles, and step edges, whereas Δ2 remains robust. This indicates that the two superconducting gaps respond differently to such 1D defects. High-resolution measurement using a Pb-coated tip reveals localized in-gap states near 1D defects, indicating possible defect-induced magnetism. Our findings highlight the contrasting behaviors of gap Δ1 and gap Δ2 in response to local electronic and magnetic environments and provide real-space evidence for orbital-selective superconductivity.