Anomalous ground states at the interface between two transition-metal compounds

The effects of strong covalency across a strongly correlated interface between two transition-metal compounds are studied. Since the charge transfer is directional, the lowest electron-removal and -addition states are often not involved in the formation of covalent bonds across the interface. This paper shows that this can lead to the formation of unusual ground states not found in the bulk. For cuprates, the formation of “Zhang-Rice triplets” is observed. For nickelates, we demonstrate the possibility of in-plane or out-of-plane orbital switching, whereas cobaltates are prone to spin switching. For Co and Fe compounds, a change between antiferromagnetic superexchange and ferromagnetic double exchange is found. Calculations of x-ray magnetic dichroism are presented, which could provide insight into the presence of these unusual ground states.