LaAlO3 and SrTiO3 are ordinary insulators, but when an atomically sharp interface is formed between them, the interface can conduct, magnetize, or even superconduct. Control over such interface properties could lead to novel artificial nanoscale materials.
Depending on precise atomic registry, there are in fact two distinct LaAlO3/SrTiO3 interfaces.Â The n-type presents all the exciting behaviors while the p-type shows no conductivity or unusual behavior. First principles theory allows us to see and understand this asymmetry. Below, we show the carrier distributions about the interfaces. For the n-type, the carriers are bound to the interface so the interface isÂ conducting. For p-type the carriers delocalize into the SrTiO3 substrate and the interface remains insulating. The unusual quantum coupling between La and Ti atoms that binds electrons at the n-type interface is general and applies to other oxide interfaces.