Abstract Body

Since the discovery of superconductivity in infinite-layer nickelates [1], investigations into the superconducting mechanism have been undertaken, focusing on both similarities and differences compared to unconventional superconductors. In nickelates, distinctions from cuprates have been explored, including the multi-orbital nature originating from rare-earth 5d orbitals [2], the absence of Mott insulating behavior in the parent compound [3], and the lack of antiferromagnetic long-range order [4]. However, for nickelate thin films obtained through topochemical reduction reactions, the range of applicable experimental methods is limited. Within this context, comprehending and advancing the synthesis process of nickelate superconductors is believed to hold a significant position in elucidating the mechanism of superconductivity.

In this presentation, building upon our recent understanding of aspects shared and divergent from the cuprates, we will discuss our recent advancements in topochemical reduction. This process selectively removes apical oxygens from the NiO₆ octahedra within the precursor perovskite phase. Through precise control of the reduction temperature, we have successfully enhanced the superconducting properties of La_1-xSr_xNiO₂ [5]. Beyond discussing these enhancements in superconducting properties, we will also discuss the recent progress in the superconducting properties of nickelates.

References

[1] D. Li et al., Nature 572, 624 (2019).
[2] D. Li et al., Phys. Rev. Lett. 125, 147003 (2020).
[3] K.-W. Lee and W. E. Pickett, Phys. Rev. B 70, 165109 (2004).
[4] M. Hayward and M. Rosseinsky, Solid. State Sci. 5, 839 (2003).
[5] M. Osada et al., Phys. Rev. Mater. 7, L051801 (2023).