![]() ![]() The XRD characterization of the as-grown perovskite Nd 0.8Sr 0.2NiO 3 thin films can be found in Supplementary Fig. In this work, we comprehensively investigate the Nd 0.8Sr 0.2NiO 2 films of various thicknesses to confirm the bulk nature of the superconductivity and reveal the interfacial effects on the multiband picture of the infinite-layer nickelate thin films and demonstrate their perfect DC diamagnetic response.įigure 1a shows the X-ray diffraction (XRD) θ–2 θ patterns of the Nd 0.8Sr 0.2NiO 2 thin films of different thicknesses from 4.6 to 15.2 nm. This further adds to the puzzle of whether the observed electronic properties are associated with the bulk or the heterostructure interface. Theoretical calculation further proposed that the interface/surface-induced Fermi surface modification causes the transformation from a d-wave paring in bulk into an s-wave paring at the interface/surface 2, 17, which might be consistent with the recent observation of two gaps from the tunneling spectrum measurement 5. These beg the question of whether the superconductivity occurs in the whole film or at the interface between the nickelate and SrTiO 3 (STO) substrate 13, 14, 15, 16. Moreover, the DC diamagnetic response in the superconducting thin films has never been demonstrated 1. In contrast, infinite-layer nickelates prepared in bulk form show only insulating behavior 10, 11, 12. Numerous theoretical works have been conducted based on the bulk pictures 2 however, the superconductivity has only been observed in epitaxial Nd 1-xSr xNiO 2 and Pr 1-xSr xNiO 2 ultrathin films (up to ~10 nm) with an infinite-layer structure 1, 3, 4, 5, 6, 7, 8, 9. However, the recent results indicate the complex multiband structures in doped infinite-layer nickelates, suggesting a new family of superconductivity 1, 2. ![]() The search for the nickelate superconductivity was enthused by the idea of mimicking the \(3\,\)orbital of the single-band high- T c cuprates 1. ![]() Consistent with band structure calculations on the nickelate/SrTiO 3 heterostructure, the interface and strain effect induce a dominating electron-like band in the ultrathin film, thus causing the sign-change of the Hall-coefficient. Moreover, X-ray absorption spectroscopy reveals the Ni-O hybridization nature in doped infinite-layer nickelates, and the hybridization is enhanced as the thickness decreases. Unlike the thick films in which the normal-state Hall-coefficient changes signs as the temperature decreases, the Hall-coefficient of films thinner than 5.5 nm remains negative, suggesting a thickness-driven band structure modification. Perfect diamagnetism is achieved, confirming the occurrence of superconductivity in the films. Here, we show high-quality Nd 0.8Sr 0.2NiO 2 thin films with different thicknesses and demonstrate the interface and strain effects on the electrical, magnetic and optical properties. However, material synthesis remains challenging, direct demonstration of perfect diamagnetism is still missing, and understanding of the role of the interface and bulk to the superconducting properties is still lacking. The recent discovery of superconductivity in the infinite-layer nickelate thin films has fulfilled this pursuit. They may provide clues towards understanding the mechanism and an alternative route for high-temperature superconductors. Nickel-based complex oxides have served as a playground for decades in the quest for a copper-oxide analog of the high-temperature superconductivity. ![]()
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