Creating emergent phenomena in oxide superlattices

Complex oxides are record holder materials for many phenomena, including ferroelectricity, piezoelectricity, superconductivity and multiferroicity. Complex oxides often have competing ground states with energies slightly higher than that of the true ground state. This competition is fortuitous because thermodynamic variables (for example, temperature, electric field, magnetic field, stress and chemical potentials) can access these metastable phases that are usually hidden but emerge as the energetic landscape is reshaped by adjusting the thermodynamic variables. Epitaxial superlattices are a platform for imposing thermodynamic boundary conditions to unleash the properties of hidden phases by altering the delicate balance between competing spin, charge, orbital and lattice degrees of freedom. Additionally, a feature of complex oxides with large responses (large property coefficients) is the coexistence of phases on the nanoscale. New phases can emerge at the heterointerfaces of oxide superlattices, and X-ray, electron, neutron and proximal probes as well as ab initio theoretical studies can provide insights into these emergent phenomena.