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DOE OSTI · 3362572

Hund's coupling assisted orbital-selective superconductivity in Ba1-xKxFe2As2

Corbae, Elena·Zhang, Rong·Li, Cong·Kihou, Kunihiro·Lee, Chul-Ho·Hashimoto, Makoto·Devereaux, Thomas·Tjernberg, Oscar·Babaev, Egor·Lee, Dung-Hai·Grinenko, Vadim·Lu, Donghui·Shen, Zhi-Xun
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Abstract

While the superconducting transition temperature of hole-doped Ba_{1-x}K_{x}Fe_{2}As_{2} decreases past optimal doping, superconductivity does not completely disappear even for the fully doped KFe_{2}As_{2} compound. In fact, superconductivity is robust through a Lifshitz transition where electron bands become hole-like around the zone corner at around x=0.7, thus challenging the conventional understanding of superconductivity in iron-based systems. High-resolution angle-resolved photoemission spectroscopy is used to investigate the superconducting gap structure, as well as the normal state electronic structure, around optimal doping and across the Lifshitz transition. Our findings reveal a largely orbital-dependent superconducting gap structure, where the more strongly correlated d_{xy} band has a vanishing superconducting gap at higher doping, aligning with the Hund's metal behavior observed in the normal state. Notably, the superconducting gap on the d_{xy} band disappears before the Lifshitz transition, suggesting that the Fermi surface topology may play a secondary role. We discuss how these results point to orbital-selective superconducting pairing and how strong correlations via Hund's coupling may shape superconducting gap structures in iron-based and other multiorbital superconductors.

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FOS: Physical sciencesStrongly Correlated Electrons (cond-mat.str-el)Superconductivity (cond-mat.supr-con)

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Corbae, Elena, Zhang, Rong, Li, Cong, Kihou, Kunihiro, Lee, Chul-Ho, Hashimoto, Makoto, Devereaux, Thomas, Tjernberg, Oscar, Babaev, Egor, Lee, Dung-Hai, Grinenko, Vadim, Lu, Donghui, Shen, Zhi-Xun. 2025-01-01. Hund's coupling assisted orbital-selective superconductivity in Ba1-xKxFe2As2. https://doi.org/10.48550/arxiv.2510.06435

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