Electric Polarization Switching on an Atomically Thin Metallic Oxide.

Materials with reduced dimensions have been shown to host a wide variety of exotic properties and novel quantum states that often defy textbook wisdom. Polarization switching and metallic screening are well-known examples of mutually exclusive properties that cannot coexist in bulk solids. Here we report the fabrication of (SrRuO3)1/(BaTiO3)10 superlattices that exhibits reversible polarization switching in an atomically thin metallic layer. A multipronged investigation combining structural analyses, electrical measurements, and first-principles electronic structure calculations unravels the coexistence of two-dimensional (2D) metallicity in the SrRuO3 layer accompanied by the breaking of inversion symmetry, supporting electric polarization along the out-of-plane direction. Such a 2D ferroelectric-like metal paves a novel way to engineer a quantum multistate with unusual coexisting properties, such as ferroelectrics and metals, manipulated by external fields.