Correlated phase diagram tunable by structural layering in square-planar nickelates

Since the discovery of superconductivity in Sr-doped NdNiO₂¹, the identification of independent tuning parameters has further expanded the materials and correlated phases in this family of nickel-based compounds. One such knob has been the structural layering, which has been used to realize a superconducting phase in the five-layer square-planar nickelate Nd₆Ni₅O₁₂². In the square-planar Nd_n+1Ni_nO_2n+2 compounds the primary role of layering is to provide a nominal doping level of 1/n electrons per nickel site. Nonetheless, one might expect substantial modification of the electronic structure, correlation effects, or even nominal doping levels from intentional restructuring of the atomic lattice. Here, we present the correlated phase diagram of the layered Nd_n+1Ni_nO_2n+2 compounds. We observe a superconducting dome of clear resemblance to the chemically doped infinite-layer nickelates, indicating that structural layering can generally tune the electronic doping levels. This furthermore supports the potential universality of doping-dependent superconducting phases^3–6. We discuss the role of layering beyond providing rigid doping shifts, including effects on correlations, spin fluctuations, and disorder.



References:

1. Li, D. et al. Nature 572, 624–627 (2019). 2. Pan, G. A. et al. Nat. Mater. 21, 160–164 (2022). 3. Lee, K. et al. Nature 619, 288–292 (2023). 4. Keimer, B., Kivelson, S. A., Norman, M. R., Uchida, S. & Zaanen, J. Nature 518, 179–186 (2015). 5. Johnston, D. C. Adv. Phys. 59, 803–1061 (2010). 6. Cao, Y. et al. Nature 556, 43–50 (2018).