Ni1+𝛿 metallic state and purely Ni−𝑑𝑥2−𝑦2-occupied Fermi surface in SrNiO2-based superlattices at ambient pressure

Ni1+𝛿 metallic state and purely Ni−𝑑𝑥2−𝑦2-occupied Fermi surface in SrNiO2-based superlattices at ambient pressure

Physical Review Materials

10.1103/PhysRevMaterials.9.044802

https://doi.org/10.1103/physrevmaterials.9.044802

Miao Li, Zhenyu Ding, Yuqiang Liu, Liangyu Li, Gang Wu, Xiaoping Yang

General Materials Science

21 April 2025

Li, M., Ding, Z., Liu, Y., Li, L., Wu, G., & Yang, X. (2025). Ni1+𝛿 metallic state and purely Ni−𝑑𝑥2−𝑦2-occupied Fermi surface in SrNiO2-based superlattices at ambient pressure. Physical Review Materials, 9(4). https://doi.org/10.1103/physrevmaterials.9.044802

The rich physics of nickelates has garnered widespread attention, particularly for their superconductivity and the prominent Ni−𝑑𝑥2−𝑦2-dominated Fermi surface. Motivated by the Ni1+𝛿 superconductivity in infinite-layer NdNiO2 (𝑇𝑐=15K) and high-pressure superconducting La3⁢Ni2⁢O7 (𝑇𝑐=80K), we designed a (SrNiO2)2/(LaTiO3)1 superlattice with a two-dimensional confined bilayer NiO2. LaTiO3 acts as an electron donor, transferring a full electron to the NiO2 double layers due to the electronegativity difference between Ni(1.91) and Ti(1.54). This charge transfer transforms the Fermi surface from a multiorbital character, resembling that of NdNiO2, into one dominated purely by Ni1+𝛿−𝑑𝑥2−𝑦2 orbitals. Factors that limited the transition temperature in NdNiO2, such as 5⁢𝑑−3⁢𝑑 hybridization, self-doping between Nd and Ni atoms, and the weak 𝑝−𝑑 hybridization between Ni and O atoms, are effectively suppressed and enhanced, respectively. The nearest-neighbor 𝑒𝑔 hoppings closely resemble those in undoped infinite-layer NdNiO2, though they are smaller than those found in high-pressure La3⁢Ni2⁢O7. Similar to La3⁢Ni2⁢O7, this superlattice exhibits a low-spin magnetic state with instability stemming from nearly degenerate magnetic ground states. Additionally, F doping in NiO2 double layers can be used to fine tune the Ni valence state and the magnetic coupling, simulating the effects of oxygen pressure in the preparation. Our research offers new insights into the mechanisms driving high-𝑇𝑐 superconductivity in nickelates under ambient pressure, emphasizing the pivotal role of heterostructure engineering in these processes.

Publisher Copyright

This research / project is supported by the A*STAR - RIE2025 MANUFACTURING, TRADE AND CONNECTIVITY (MTC) PROGRAMMATIC FUND
Grant Reference no. : M24M8b0004

https://oar.a-star.edu.sg/communities-collections/articles/23013

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