Discovering, Understanding and Predicting Emergent Phenomena at Strongly Correlated Oxide Interfaces.

摘要

Transition metal oxides are strongly correlated electron systems, with behavior controlled by subtle compromises between different competing states which gives the oxides a heightened sensitivity to external perturbations, like pressure or applied fields. Our goal here is to develop layered oxide analogs of lattice-matched perovskites that offer increased oxygen stability, higher carrier densities, and an intrinsically reduced dimensionality through a layered internal structure that should help to stabilize emergent interface phenomena resulting from the competition between closely-confined ground states. We have succeeded in defect-engineering the Ruddlesden-Popper (RP) system to reduce dielectric losses and identified dynamical rearrangements during growth of the RP layers that can be tuned to improve growth quality. Likely other oxide systems, whose performance in thin film form is limited by point defects, could also be greatly enhanced with similar defect engineering. We show that cation defects in LaAlO3 can control the formation of a two-dimensional electron liquid at the LaAlO3/SrTiO3 interface. We identify infinite-layer cuprates as a promising materials family for bipolar heterostructure devices in correlated oxide electronics, and grow high quality thin films that allow us to address a long-standing discrepancy in the asymmetry between electron and hole doping in high-temperature cuprate superconductivity.