  In pursuit of creating cuprate-like electronic and orbital structures,
artificial heterostructures based on LaNiO$_3$ have inspired a wealth of
exciting experimental and theoretical results. However, to date there is a very
limited experimental understanding of the electronic and orbital states
emerging after interfacial charge-transfer and their connections to the
modified band structure at the interface. Towards this goal, we have
synthesized a prototypical superlattice composed of correlated metal LaNiO$_3$
and doped Mott insulator LaTiO$_{3+\delta}$, and investigated its electronic
structure by resonant X-ray absorption spectroscopy combined with X-ray
photoemission spectroscopy, electrical transport and theory calculations. The
heterostructure exhibits interfacial charge-transfer from Ti to Ni sites giving
rise to an insulating ground state with orbital polarization and $e_\textrm{g}$
orbital band splitting. Our findings demonstrate how the control over charge at
the interface can be effectively used to create exotic electronic, orbital and
spin states.
