Designing novel materials whose functionalities are set by the epitaxial construction has become possible thanks to the recent development in theoretical calculation methods and thin film deposition. One proposition, particularly relevant to the perovskite structure, is to couple the rotations and tilts of the oxygen octahedra in epitaxial heterostructures to promote new electronic and magnetic states.
In a particular set of octahedra rotations (labeled as a–a–c+ in the Glazer notation), the A cations of the ABO3 perovskite move in an alternate fashion between consecutive (001) planes. This antipolar mode can be converted into a polar one by breaking the crystal symmetry: this can be achieved alternating layers with different A cations using thin film deposition. We are currently investigating this improper ferroelectric state, which is predicted to occur in several insulating orthorhombic multilayers, in vanadate heterostuctures  grown by pulsed laser deposition. Performing advanced structural measurements with X-ray diffraction and scanning transmission electron microscopy, we are probing the coupling of the structural distortions across the different layers and the chemical intermixing occurring across the interfaces.
The research is performed in collaboration with the ab-initio theory group of Philippe Ghosez at the University of Liège (B) and with the scanning transmission electron microscopy team of D. Alexander at EPFL (CH).