IISER MOHALI

Abstract: Interface engineering involves conscious manipulation and control of the interactions between different materials at their interfaces. It is instrumental in bringing forth diverse novel phenomena. A ferroelectric material surface accumulates uncompensated bound charges resulting in a depolarisation field opposite to the spontaneous polarisation. The electric polarisation suppresses below the critical thickness of a ferroelectric material. The existence of critical thickness hampers the growth of low-power compact ferroelectric memories. Here, we demonstrate bulk-like ferroelectricity in ultrathin regime (down to a single unit cell of BTO) in epitaxially grown La0.7Sr0.3MnO3 (LSMO)-BaTiO3 (BTO) superlattices via the deterministic control both above and underneath the ferroelectric. However, the bilayer of LSMO-BTO becomes paraelectric below 5 unit cells, as previously reported. Second harmonic generation and piezo response microscopy illustrate the breaking of inversion symmetry and switchable polarisation. Reciprocal space mapping techniques confirm the strain evolution in the superlattices. With density functional theory calculations, we prove that the interface charges at LSMO layer terminations can cooperatively sustain polarisation, precluding the including LSMO-SrTiO3 and LaMnO3-BTO, thereby sustaining the ferroelectric phase in bulk paraelectric SrTiO3 and BTO, indicating the possible absence of critical thickness in perovskites, enabling ultralow-dimension future ferroelectric memory devices.