Polar NaTaO3/LaAlO3 (001) superlattices: A comparison of PBEsol and PBEsol+U first-principles calculations

The increasing experimental and theoretical interest in two-dimensional charge carrier gases formed at the interfaces of heterostructured perovskite oxide systems has led to a demand for a deeper understanding regarding the influence of exchange–correlation functionals and associated corrections on the systems’ properties. Herein, we investigate the impact of implementing additive Hubbard corrections compared to standard DFT routines using the PBEsol functional in polar NaTaO3/LaAlO3 (001) superlattices. Structural analysis reveals that the qualitative assessment remains consistent regardless of the approach, with slight variations observed for the NaTaO3 phase due to more pronounced polar distortions. Electronically, standard PBEsol fails to accurately describe the electronic structure of the superlattice below the system’s critical thickness, whereas the inclusion of on-site Coulomb interactions through PBEsol+U routines provides the correct semiconductor character of the superlattice, emphasizing the role of strong correlation effects on d and f electrons at the material’s interface. Additionally, our investigation reveals the spatial charge separation in the semiconductor heterostructure, with potential implications for photocatalytic devices. This work not only contributes to demonstrate the importance of the chosen methodology when studying such systems but also sheds light on important electronic and structural properties of NaTaO3/LaAlO3 (001) superlattices, enabling new avenues for future applications.