Synergistic polar states by selective atomic gradients

Materials that combine distinct properties within a single phase are of fundamental and technological interest. Here, we present a broadly applicable strategy to achieve strong bulk polarity that not only coexists with its originally incompatible properties, such as metallicity, but also synergistically enables exceptional functionalities. A combination of thin-film synthesis, atomic-scale imaging, and theoretical calculations reveals that A-site selective atomic gradients induce strong polar states in otherwise centrosymmetric perovskite oxides ABO₃. These polar states unconventionally coexist with various preexisting properties, leading to bulk polar metallicity with tunable nonreciprocal transport; high-κ, low-loss dielectricity with an equivalent oxide thickness below 0.1 nanometer; and giant pyroelectricity. This work may enable the development of new multifunctional materials with unusual coexisting and synergistic properties.