Asymmetric ferroelectricity by design in atomic-layer superlattices with broken inversion symmetry

One hundred years after ferroelectricity was first reported [Physical Review 17, 475 (1921)], a qualitatively different phenomenon, asymmetric ferroelectricity, is reported in atomic-scale engineered crystals. Unlike the high-temperature centrosymmetric structure that prevail in ferroelectric crystals, the crystals here break inversion symmetry by design. This is achieved by sequenced stacking of three molecular components. When these tailored crystals become hysteretic below an ordering temperature, two unequal polarization states emerge. This unusual bistability points to an asymmetric energy landscape, controlled by sample architecture.