  The breaking of orbital degeneracy on a transition metal cation and the
resulting unequal electronic occupations of these orbitals provide a powerful
lever over electron density and spin ordering in metal oxides. Here, we show
how to dynamically modulate the orbital populations on Mn atoms at
ferroelectric/manganite interfaces by switching the ferroelectric polarization.
The change in orbital occupation can be as large as 10\%, greatly exceeding
that of bulk manganites. This flippable orbital splitting is in large part
controlled by the propagation of ferroelectric polar displacements into the
interfacial region, a structural motif absent in the bulk and unique to the
interface. We use {\it ab initio} theory, epitaxial thin film growth, and
scanning transmission electron microscopy to verify the predicted interfacial
polar state and concomitant orbital splittings.
