Electrical transport and dimensionality control in infinite-layer nickelates

The discovery of Ni-based superconductors has brought new hope to the field of high-temperature superconductivity. Understanding the dimensional characteristics and anisotropy of nickelate superconductors has become a central focus in current research. However, the nature of the nickelate superconductivity, especially the transition between 2D and 3D superconductivity, remains debated. In this study, we investigated the magnetic field-dependent electrical transport behaviors of infinite-layer nickelates. The La0.8Sr0.2NiO2 films exhibit highly anisotropic superconductivity, which fits well with the 2D Tinkham model, indicating a purely 2D superconducting nature. In contrast, the Nd0.8Sr0.2NiO2 films show isotropic behavior with a mixed 2D + 3D superconducting characteristics. This “mixed 2D + 3D superconducting behavior” is typically associated with the complexity of the electronic band structure in the material. Through a systematic comparison of two model systems with distinct rare-earth orbital contributions, we propose a new perspective based on orbital selectivity. The observed difference likely originates from Nd0.8Sr0.2NiO2 incorporates the Nd 5dz2 orbital, adding a 3D component. Its interaction with the Ni 3dx2−y2 orbital leads to orbital-selective pairing. Theoretical calculations provide key evidence that the Nd-based system exhibits greater isotropy and 3D character compared to the La-based system. Our study thus suggests that orbital selectivity serves as a critical mechanism governing the superconducting properties, and the distinction between rare-earth elements (such as La and Nd) ultimately influences the dimensional characteristics of superconductivity through this mechanism.