Strain Gradient Elasticity in SrTiO₃ Membranes: Bending versus Stretching

Young's modulus determines the mechanical loads required to elastically stretch a material, and also, bend it, given that bending stretches one surface while compressing opposite one. Flexoelectric materials have additional property of becoming electrically polarized when bent. While numerous studies characterized this flexoelectric coupling, its impact on response, due energy cost polarization upon bending, is largely unexplored. This intriguing contribution strain gradient elasticity expected become visible at small length scales where gradients are geometrically enhanced, especially in high permittivity insulators. Here we present nano-mechanical measurements freely suspended SrTiO3 membrane drumheads. We observe striking non-monotonic thickness dependence deflections. Furthermore, inferred from predominantly deformation three times larger than stretching for membranes thinner 20 nm. In regime extract giant elastic coupling ~2.2e-6 N, which could be used new operational regimes nano-electro-mechanics.