| Abstract Scope |
I will discuss the experimental observation of “asymmetric ferroelectricity”, an electronic property not found in natural crystals, accomplished in atomic-layer superlattices where the atomic-layer stacking sequence of three constituent phases, CaTiO<sub>3</sub>, SrTiO<sub>3</sub>, and BaTiO<sub>3</sub>, is tailored to break inversion symmetry. The nanostructured asymmetric strain programmed into these crystals via the stacking order removes the symmetry that would otherwise exist at high temperatures, resulting in an electronically polarized sample where polarization increases as the temperature is lowered. In contrast to a ferroelectric characterized by a bistable ground state with two equal and opposite polarizations, these nanostructured crystals bear asymmetric ferroelectric correlations<sup>§</sup> that develop below a temperature T<sub>x</sub>. Both magnitude and direction of this ferroelectric asymmetry can be controlled using monolayer stacking order. Experimental evidence will be presented, suggesting that the correlated dipole units are mesoscale nanocolumns extending through the film thickness at low temperatures.
<sup>§</sup>Phys. Rev. B. 104, 085103 (2021) |