Competition between ground states at phase boundaries can lead to significant changes in materials properties under stimuli, particularly when these ground states have different crystal symmetries. A key challenge is to stabilize and control coexistence of symmetry-distinct phases. Using BiFeO₃ (BFO) layers confined between layers of dielectric TbScO₃ (TSO) as a model system, we stabilize the mixed phase coexistence of emergent centrosymmetric and non-centrosymmetric BFO phases at room temperature with antipolar, insulating and polar, semiconducting behavior, respectively. Application of orthogonal in-plane electric (polar) fields results in reversible nonvolatile interconversion between the two phases, hence removing and introducing centrosymmetry. Counterintuitively, we find that an electric field ‘erases’ polarization, resulting from the anisotropy in octahedral tilts introduced by the interweaving TSO layers. Consequently, this interconversion between centrosymmetric and non-centrosymmetric phases generates changes in non-linear optical response of over three orders-of-magnitude, resistivity of over five orders-of-magnitude, and control of microscopic polar order. Our work establishes a platform for cross-functional devices that take advantage of changes in optical, electrical, and ferroic responses, and demonstrates octahedral tilts as an important order parameter in materials interface design.
Lucas Caretta is an Assistant Professor in the School of Engineering at Brown University. From atoms to devices, Caretta research focuses on the design, discovery, and development of novel physics in complex oxide thin films for next generation memory and logic, sensing, and even energy conversion. His comprehensive research approach combines epitaxial, atomic-scale thin film synthesis and state-of-the-art in-situ materials characterization. Ultimately, he aims to solve fundamental nanoscale problems which tackle technological large scale challenges. Before Brown, Caretta was a University of California (UC) President’s Postdoctoral Fellow and a Ford Foundation Postdoctoral Fellow at UC Berkeley working with Professor Ramamoorthy Ramesh. At Berkeley, Caretta studied emergent phenomena in epitaxial multiferroic and magnetic heterostructures and superlattices. He completed his Ph.D. in Materials Science and Engineering at the Massachusetts Institute of Technology as a National Science Foundation Graduate Research Fellow and a GEM Consortium Fellow under the guidance of Professor Geoffrey Beach. There, he made significant contributions to the understanding of magnetic soliton dynamics in compensated systems.