We employ density functional theory in combination with a correlation U correction to elucidate a complete charge transfer phenomenon between the interfacial Ti-t_2g orbitals and Ir-t_2g orbitals within spin–orbit-coupled (SrIrO₃)_m/(LaTiO₃)₁ superlattices. This charge transfer is driven by the interfacial polarity difference and oxygen octahedral distortion. Our investigation shows that hole doping of the LaTiO₃ layer or increasing the number m of SrIrO₃ layers offers an effective means to modulate the charge transfer and the electron occupation within the J_eff = 1/2 5d-bands of Ir atoms. This modulation leads to the emergence of various electronic states, including nonmagnetic band insulating (SrIrO₃)₁/(LaTiO₃)₁, ferromagnetic metallic (SrIrO₃)₁/(La_1–xBa_xTiO₃)₁, ferrimagnetic Mott insulating (SrIrO₃)₂/(LaTiO₃)₁, and ferrimagnetic metallic (SrIrO₃)_m/(LaTiO₃)₁ with m ≥ 3. Notably, we find that charge transfer and the two-dimensional electron gas phenomenon occur exclusively at the interfacial IrO₂ monatomic layers of (SrIrO₃)_m/(LaTiO₃)₁, regardless of the thickness of the SrIrO₃ layer. This behavior sharply contrasts with the characteristics of the LaAlO₃/SrTiO₃ system, where the 2DEG extends across multiple unit cells. Our research provides fresh insights into the unconventional 5d electronic structures of spin–orbit-coupled iridates, particularly those with less-explored fractionally occupied mixed valence state (Ir^3.3+/Ir^3.7+), suggesting their potential for application in nanoscale oxide electronic devices.

Link to the article: https://pubs.acs.org/doi/full/10.1021/acsaelm.4c01015