Anisotropic suppression of octahedral breathing distortion with the fully strained BaBiO₃/BaCeO₃ heterointerface

While the physiochemical effects of octahedral tilting and rotating distortions have been studied extensively, octahedral breathing distortion (OBD) at heterointerfaces has rarely been explored. Here, we investigated OBD in fully strained BaBiO₃ (BBO) epitaxial films by making a new type of oxide heterointerface with non-breathing BaCeO₃ epitaxial films. The integration of first-principles calculations with experimental observations of optical spectroscopy revealed that the oxygen displacement modes in BBO became disordered within six unit cells at the heterointerface and the surface. Controlling OBD in perovskite oxide thin films provides a means to exploit emerging material properties.