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Free-Anionic Duality of Interstitial Electrons Drives Superconductivity in Electride La3In
Zhao Liu1, Xiang Wang1, Yin Yang1
1Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, Ningbo 315211, China.
None:
Electrides, featuring interstitial anionic electrons (IAEs) in lattice cavities, offer a novel platform for superconductivity research, yet their electronic behavior, nature, and role of IAEs in Cooper pairing formation remain unclear due to challenges in direct observation. Here, using angle-resolved photoemission spectroscopy (ARPES), transport measurements, and first-principles calculations, we demonstrate that IAEs in electride La3In exhibit dual anionic and near-free electron characteristics. With our established effective local potential model, we trace that IAEs are located near Fermi-level states above potential barriers, forming a Fermi sea susceptible to La-derived phonon scattering, triggering superconductivity at 9.4 K. ARPES combined with high-resolution XRD measurements on oxygen-treated samples confirms the spatial distribution and energy dispersion of IAEs, aligning with our theoretical predictions. Oxygen treatment-induced reduction of near-free electrons correlates with diminished superconductivity, directly linking IAEs to electron-phonon coupling. Our study resolves the long-standing ambiguity regarding the nature of IAEs, elucidates their role in driving phonon-mediated superconductivity, and lays the foundation for exploring electride-based superconductors.
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