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DOE OSTI · 3382434

Hund's coupling governed orbital-selective superconductivity in Ba 1−𝑥 ⁢K 𝑥⁢ Fe 2 ⁢As 2

Corbae, Elena [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)]·Zhang, Rong [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)] (ORCID:0000000237181605)·Li, Cong [KTH Royal Institute of Technology, Stockholm (Sweden)]·Kihou, Kunihiro [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)] (ORCID:0000000330654147)·Lee, Chul-Ho [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)] (ORCID:000000016918976X)·Hashimoto, Makoto [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)]·Devereaux, Thomas [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)]·Tjernberg, Oscar [KTH Royal Institute of Technology, Stockholm (Sweden)] (ORCID:0000000186696886)·Babaev, Egor [KTH Royal Institute of Technology, Stockholm (Sweden)]·Lee, Dung-Hai [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000247935829)·Grinenko, Vadim [Shanghai Jiao Tong University (China)]·Lu, Donghui [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)] (ORCID:0000000297080443)·Shen, Zhi-Xun [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)] (ORCID:0000000214540281)
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Abstract

Understanding how strong electronic correlations shape superconductivity remains a central challenge in quantum materials. In multiorbital systems, correlations driven by Hund's coupling can differentiate the behavior of individual orbitals, producing the so-called Hund's metal state. How such orbital-selectivity also governs superconducting pairing, however, has remained largely unexplored experimentally. Here, in this study, we use high-resolution angle-resolved photoemission spectroscopy to systematically map the superconducting gap structure across the phase diagram of the representative iron-based superconductor Ba 1−x K x Fe 2 As 2 . We find that superconductivity evolves in a strongly orbital-dependent manner: the gap associated with the d xy orbital collapses beyond optimal doping while pairing on the d xz /d yz orbitals persists. This behavior mirrors the orbital-selective correlations observed in the normal state and reveals a direct connection between Hund's metal physics and the superconducting pairing landscape. Our results demonstrate that superconducting gaps themselves can serve as a sensitive probe of orbital-dependent correlations and suggest that Hund's coupling plays a central role in shaping pairing in multiorbital superconductors.

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Corbae, Elena [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)], Zhang, Rong [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)] (ORCID:0000000237181605), Li, Cong [KTH Royal Institute of Technology, Stockholm (Sweden)], Kihou, Kunihiro [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)] (ORCID:0000000330654147), Lee, Chul-Ho [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)] (ORCID:000000016918976X), Hashimoto, Makoto [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)], Devereaux, Thomas [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)], Tjernberg, Oscar [KTH Royal Institute of Technology, Stockholm (Sweden)] (ORCID:0000000186696886), Babaev, Egor [KTH Royal Institute of Technology, Stockholm (Sweden)], Lee, Dung-Hai [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000247935829), Grinenko, Vadim [Shanghai Jiao Tong University (China)], Lu, Donghui [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)] (ORCID:0000000297080443), Shen, Zhi-Xun [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford University, CA (United States)] (ORCID:0000000214540281). 2026-06-12. Hund's coupling governed orbital-selective superconductivity in Ba 1−𝑥 ⁢K 𝑥⁢ Fe 2 ⁢As 2. https://doi.org/10.1103/yry8-qdm6

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