Daily Overview: Today’s highlights focus on breakthrough explorations of electron doping strategies and high-field behavior in nickel-based superconducting systems. In [1], first-principles calculations systematically evaluate the feasibility of electron doping via tetravalent element substitution in bilayer Ruddlesden–Popper La₃Ni₂O₇ thin films, clearly indicating that zirconium, hafnium, and thorium can effectively introduce electron carriers and enhance the interlayer hopping of the Ni d_{z²} orbital, potentially raising the superconducting transition temperature and providing key candidate doping pathways to clarify the pairing mechanism debate. Meanwhile, in [2], a high-field-stabilized reentrant superconducting state with a transition temperature up to 40 K is observed in infinite-layer nickelate thin films. The phase diagram can be perfectly fitted by the Jaccarino-Peter field compensation mechanism, indicating that the internal exchange field provided by the introduced Eu²⁺ ions effectively suppresses Pauli paramagnetic pair breaking. This marks the first realization of such strong-field-stabilized superconductivity in high-temperature superconductors, opening new directions for exploring superconducting applications under extreme magnetic fields. arXiv submission processing window: 2026-05-29 00:00 to 2026-05-29 00:00 UTC.

1. Electron Doping of $\mathrm{La_3Ni_2O_7}$ Thin Films: Candidate Metal Dopants and Their Potential Impact on Superconductivity

Summary: This study employs first-principles density functional theory calculations to systematically investigate the feasibility of electron doping in bilayer Ruddlesden–Popper nickel oxide La₃Ni₂O₇ thin films through substitution with tetravalent elements. The results indicate that, unlike in copper oxides, cerium (Ce) doping is ineffective in introducing electron carriers into the low-energy bands, whereas zirconium (Zr), hafnium (Hf), and thorium (Th) serve as efficient electron dopants. Substitution with these elements significantly enhances the interlayer hopping integral t⊥ between Ni d_{z²} orbitals, potentially increasing the interlayer superexchange coupling J⊥ and thereby raising the superconducting transition temperature T_c. The constrained random phase approximation (cRPA) is used to evaluate the interaction parameters. This work identifies candidate dopant elements for realizing electron-doped La₃Ni₂O₇, providing a pathway to clarify the ongoing debate regarding the pairing mechanism in this system.

2. High-field-stabilized reentrant superconductivity in infinite-layer nickelate thin films

Summary: Traditional magnetic fields suppress superconductivity through Pauli and orbital effects; however, this work reports a high-field-stabilized re-entrant superconducting state in infinite-layer nickelate thin films (SECNO), with a superconducting transition temperature as high as 40 K. Through resistance measurements and analysis of the magnetic field–temperature phase diagram, the samples exhibit superconductivity under both low and high fields, and the high-field superconducting state merges with the low-field state when the magnetic field is rotated into the film plane, maintaining zero resistance up to 65 T. This behavior can be explained by the Jaccarino-Peter field compensation mechanism: doped Eu²⁺ ions generate a negative internal exchange field that partially cancels the external field, thereby suppressing Pauli pair breaking. The phase diagram is well fitted by the WHH model incorporating the internal exchange field, yielding key parameters such as the exchange field (~70 T). X-ray absorption spectroscopy confirms that approximately 67% of Eu is in the +2 valence state, consistent with the model. Compared to previously reported field-induced superconductivity, which was limited to low-Tc materials, this study achieves a significantly enhanced upper critical field in a high-temperature superconductor, providing a new pathway for developing superconducting devices under strong magnetic fields.