Engineered Kondo screening and nonzero Berry phase in SrTiO3/LaTiO3/SrTiO3 heterostructures

Controlling the interplay between localized spins and itinerant electrons at the oxide interfaces can lead to exotic magnetic states. Here we devise SrTiO3/LaTiO3/SrTiO3 heterostructures with varied thickness of the LaTiO3 layer (n monolayers) to investigate the magnetic interactions in the two-dimensional electron gas system. The heterostructures exhibit significant Kondo effect when the LaTiO3 layer is rather thin (n = 2, 10), manifesting the strong interaction between the itinerant electrons and the localized magnetic moments at the interfaces, while the Kondo effect is greatly inhibited when n = 20. Notably, distinct Shubnikov-de Haas oscillations are observed and a nonzero Berry phase of pi is extracted when the LaTiO3 layer is rather thin (n = 2, 10), which is absent in the heterostructure with thicker LaTiO3 layer (n = 20). The observed phenomena are consistently interpreted as a result of subband splitting and symmetry breaking due to the interplay between the interfacial Rashba spin-orbit coupling and the magnetic orderings in the heterostructures. Our findings provide a route for exploring and manipulating nontrivial electronic band structures at complex oxide interfaces.

Automated summary

Controlling the interaction between localized spins and itinerant electrons at oxide interfaces can result in exotic magnetic states. In this study, SrTiO3/LaTiO3/SrTiO3 heterostructures with varying thickness of the LaTiO3 layer (n monolayers) were used to investigate magnetic interactions in a two-dimensional electron gas system. Significant Kondo effect was observed when the LaTiO3 layer was thin, indicating strong interaction between itinerant electrons and localized magnetic moments at the interfaces. This effect was greatly inhibited when the LaTiO3 layer was thicker. Notably, distinct Shubnikov-de Haas oscillations and a nonzero Berry phase were observed in the thinner LaTiO3 layers, but absent in the thicker one. These phenomena were interpreted as a result of subband splitting and symmetry breaking due to the interplay between interfacial Rashba spin-orbit coupling and magnetic orderings in the heterostructures. These findings provide insights into manipulating nontrivial electronic band structures at complex oxide interfaces.