  Dynamical mean-field theory (DMFT) has been employed in conjunction with
density functional theory (DFT+DMFT) to investigate the metal-insulator
transition (MIT) of strongly correlated $3d$ electrons due to quantum
confinement. We shed new light on the microscopic mechanism of the MIT and
previously reported anomalous subband mass enhancement, both of which arise as
a direct consequence of the quantization of V $xz(yz)$ states in the SrVO$_3$
layers. We therefore show that quantum confinement can sensitively tune the
strength of electron correlations, leading the way to applying such approaches
in other correlated materials.
