Facet-Engineered Flexoelectricity of Centrosymmetric Semiconductors

The establishment and control of electromechanical polarization in centrosymmetric materials have been a long-standing challenge in condensed matter physics. While flexoelectricity enables polarization through strain gradients, the induced charge response is still severely limited due to the weak flexoelectric coefficient (pC/m). Here, by crystal facet engineering of lattice symmetry-breaking, we achieve precise tuning of electromechanical polarization across nearly three orders of magnitude in centrosymmetric rutile titanium dioxides without extra external fields or chemical doping. The underlying insight highlights that facet-dependent effective carrier mass mediates mobility anisotropy, which in turn governs the strain-gradient-induced charge redistribution critical for flexoelectric polarization. Furthermore, we demonstrate that crystal facet engineering enhances electromechanical polarization across diverse material systems, spanning wide-bandgap semiconductor to perovskite-based compound. This facet-driven symmetry-breaking approach extends material-by-design strategies for centrosymmetric semiconductors and programmable electromechanical devices including flexible electronics and energy harvesters.