Emergent altermagnetism in (LaVO${}_3$)${}_n$/(LaNiO${}_3$)${}_m$ superlattices from interfacial charge transfer and octahedral tilts

Using first-principles calculations, we show that altermagnetism emerges in (LaVO${}_3$)${}_n$/(LaNiO${}_3$)${}_m$ superlattices, with $(n,m)=(1,1),(2,2)$ and $(2,4)$, from the interplay of interfacial charge transfer and octahedral tilts. Charge transfer drives the system towards the V${}^{4+}$ and Ni${}^{2+}$ configuration, turning the otherwise paramagnetic nickelate layers into a magnetically active sublattice. The resulting $C$-type antiferromagnetic order, combined with $a^{-}{b}^{+}{c}^{-}$ or $a^{-}{b}^{-}{c}^{-}$ octahedral tilts, links opposite-spin sublattices only through nonsymmorphic operations, yielding a $d$-wave spin splitting without spin-orbit coupling. Within DFT+U, the splitting reaches 118 meV in the insulating (LVO)${}_1$/(LNO)${}_1$ superlattice, about twice that calculated for bulk LaVO${}_3$, and decreases as the nickelate layers become thicker. Our findings indicate that this splitting is hosted by both the V and Ni sublattices, with nearly half of its weight on oxygen $2p$ states through $p$-$d$ covalency. Interfacial charge transfer thus emerges as a $\mathit{\text{design}}$ principle for engineering altermagnetism in oxide heterostructures.