Evidence for antipolar displacements in NaNbO3 thin films. - Schneider, Thorsten; Cardoletti, Juliette; Ding, Hui; Zhang, Mao-Hua; Jiang, Tianshu; Major, Márton; Komissinskiy, Philipp; Molina-Luna, Leopoldo; Alff, Lambert (Applied Physics Letters, 2022)