Unraveling interfacial strain and interfacial lattice reconstruction mechanism of ultrathin LaMnO_(3+δ) layers in LaMnO_(3+δ)/SrTiO_3 superlattices

摘要

Understanding the interfacial lattice-reconstruction mechanism is a crucial step to purposely design functional oxide interfaces with emergent properties. Here we propose an approach using Poisson's ratio to determine the interfacial strain and unravel the underlying mechanism of lattice distortions of ultrathin LaMnO_(3+δ) layers interposed in short period (LaMnO_(3+δ))_N/(SrTiO_3)_(N(2)) superlattices. The lattice structure of a virtual bulk, with identical stoichiometry to the LaMnO_(3+δ) interfacial layer, was derived using Poisson's ratio. Thus the quantitative biaxial strain and the hydrostatic strain were obtained. Moreover, we found that changes of octahedral rotations along the in-plane and out-of-plane directions are roughly compensated, and the average rotation angle is always close to that of the virtual bulk. The study demonstrates the importance of using Poisson's ratio to understand the lattice reconstruction mechanism near oxides' interface.