  Control of structural couplings at the complex-oxide interfaces is a powerful
platform for creating new ultrathin layers with electronic and magnetic
properties unattainable in the bulk. However, with the capability to design and
control the electronic structure of such buried layers and interfaces at a
unit-cell level, a new challenge emerges to be able to probe these engineered
emergent phenomena with depth-dependent atomic resolution as well as element-
and orbital selectivity. Here, we utilize a combination of core-level and
valence-band soft x-ray standing-wave photoemission spectroscopy, in
conjunction with scanning transmission electron microscopy, to probe the
depth-dependent and single-unit-cell resolved electronic structure of an
isovalent manganite superlattice [Eu0.7Sr0.3MnO3/La0.7Sr0.3MnO3]x15 wherein the
electronic-structural properties are intentionally modulated with depth via
engineered oxygen octahedra rotations/tilts and A-site displacements. Our
unit-cell resolved measurements reveal significant transformations in the local
chemical and electronic valence-band states, which are consistent with the
layer-resolved first-principles theoretical calculations, thus opening the door
for future depth-resolved studies of a wide variety of hetero-engineered
material systems.
