Abstract Body

The discovery of superconductivity in cuprates with a critical temperature above 30 K has sparked extensive research into this family of materials. Not long after, nickelate compounds with Ni1+ ions were proposed to be the “cousin” of cuprates due to their similar electronic structures. This naturally led us to believe that the nickelates might also possess high-Tc superconductivity. Decades of research followed in search of superconducting nickelates, and in 2019, superconductivity was finally discovered in the nickelate thin films with an infinite-layer structure, Nd0.8Sr0.2NiO2, which requires complicated sample growth methodologies [1-3]. Since then, the nickelate superconductors have attracted attention and fueled lots of investigations, not to mention the boost by the latest discovery of bulk superconducting nickelates under pressure. In this talk, the recent advances in different nickelate superconductor families will be introduced. Particularly intriguing is the magnetotransport data, which has revealed a puzzling violation of the Pauli limit in the upper critical field of La-based nickelates [4]. To shed light on this phenomenon, we have meticulously measured the temperature dependence of self-field critical current density (Jc) and analyzed the data within a theoretical framework of superconductors in the thin-film limit [5], seeking clues on the possible SC pairing mechanism. Furthermore, the in-plane magnetic field angular dependence of Jc in different nickelate compounds will be discussed. These samples have demonstrated different degrees of unexpected C2 rotational symmetry in addition to the anticipated C4 symmetry dictated by the crystal symmetry [6,7]. These remarkable features exhibited by infinite-layer nickelate superconductors has urged the continued explorations in order to reveal the whole picture of SC in these systems. This work is in collaboration with Km Rubi, M. Pierre, Z. T. Zhang, T. Heil, J. Deuschle, P. Nandi, S. K. Sudheesh, Z. S. Lim, Z. Y. Luo, M. Nardone, A. Zitouni, P. A. van Aken, M. Goiran, Maxime Leroux, S. K. Goh, W. Escoffier, Changjian Li, and Neil Harrison.

References

[1] D. Li et al., Nature 572, 624-627 (2019)

[2] S. Zeng et al., Phs. Rev. Lett. 125, 147003 (2020)

[3] S. Zeng et al., Sci. Adv. 8, eabl9927 (2022)

[4] L. E. Chow, KYY et al., arXiv:2301.07606 (2023)

[5] E. F. Talantsev & J. L. Tallon, Nat. Commun. 6, 7820 (2015)

[6] L. E. Chow et al., arXiv:2201.10038 (2022)

[7] L. E. Chow, Km Rubi, KYY et al., arXiv:2301.07606 (2023)

Figure 1. Field-temperature phase diagrams of infinite-layer nickelates, indicating violation of Pauli-limit in La-based nickelates. The x- and y-axes are normalized to the Tc for easier comparisons between different systems. Figure adapted from [4].

Keywords: Infinite layer nickelates, superconductivity, electronic transport