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arXiv · 2506.16384

Real-space visualization of orbital-selective superconductivity in FeSe

Sang Yong Song·Gábor B. Halász·Jiaqiang Yan·Benjamin J. Lawrie·Petro Maksymovych
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Abstract

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 $Δ_1$ and small $Δ_2$ superconducting gaps remain nearly unchanged at the top Se sites as the STM tip approaches atomic contact. In contrast, the spectral weight of $Δ_2$ increases significantly at the Fe and bottom Se sites. These results suggest that the gap $Δ_2$ 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 $Δ_1$ near one-dimensional (1D) defects such as twin boundaries, wrinkles, and step edges, whereas $Δ_2$ 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 $Δ_1$ and gap $Δ_2$ in response to local electronic and magnetic environments and provide real-space evidence for orbital-selective superconductivity.

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Sang Yong Song, Gábor B. Halász, Jiaqiang Yan, Benjamin J. Lawrie, Petro Maksymovych. 2025-06-19. Real-space visualization of orbital-selective superconductivity in FeSe. https://arxiv.org/abs/2506.16384

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