Effect of Stoichiometry and Strain on the Stabilization of Infinite-Layer Nickelates*

Following the discovery of superconductivity in infinite-layer nickelates,¹ the degree to which these nickelates can be considered an analog material for the unconventional cuprate superconductors remains an important question. While notable experimental distinctions – for example, in the ground state of the non-superconducting regions of the superconducting phase diagram – have been made, whether these distinctions are intrinsically tied to the multi-band nature of the nickelates or extrinsically driven by crystallinity limitations has remained unclear.^2-4 In this context, significant improvement in the materials control of these thermodynamically unstable infinite-layer nickelates is of utmost importance. Following the recent breakthrough in the crystallinity of Nd_1–xSr_xNiO₂ (x = 0.05-0.325) thin films,⁵ we discuss the detailed optimization of the two-step stabilization of this material. In particular, we reveal how two key factors – cation stoichiometry and epitaxial strain – significantly influence the crystallinity and the resultant transport properties of these infinite-layer nickelates. Systematic structural and transport characterizations of these infinite-layer nickelate thin films will also be discussed in detail.

1.  D. Li et al., Nature 572, 624 (2019).

2.  A. S. Botana & M. Norman, Phys. Rev. X 10, 011024 (2020).

3.  D. Li et al., Phys. Rev. Lett. 125, 027001 (2020).

4. K. Lee et al., APL Mater. 8, 041107 (2020).

5. K. Lee et al., arXiv:2203.02580 (2022).