  Dimensional confinement has shown to be an effective strategy to tune
competing degrees of freedom in complex oxides. Here, we achieved atomic
layered growth of trigonal vanadium sesquioxide (V2O3) by means of
oxygen-assisted molecular beam epitaxy. This led to a series of high-quality
epitaxial ultrathin V2O3 films down to unit cell thickness, enabling the study
of the intrinsic electron correlations upon confinement. By electrical and
optical measurements, we demonstrate a dimensional confinement-induced
metal-insulator transition in these ultrathin films. We shed light on the
Mott-Hubbard nature of this transition, revealing an abrupt vanishing of the
quasiparticle weight as demonstrated by photoemission spectroscopy.
Furthermore, we prove that dimensional confinement acts as an effective
out-of-plane stress. This highlights the structural component of correlated
oxides in a confined architecture, while opening an avenue to control both
in-plane and out-of-plane lattice components by epitaxial strain and
confinement, respectively.
