In situ angle-resolved photoemission spectroscopy (ARPES) has been performed on SrVO3 ultrathin
films, which show metallic quantum well (QW) states, to unveil the origin of the anomalous mass
enhancement in the QW subbands. The line-shape analysis of the ARPES spectra reveals that the strength
of the electron correlation increases as the subband bottom energy approaches the Fermi level. These results
indicate that the anomalous subband-dependent mass enhancement mainly arises from the quasi-onedimensional
character of confined V 3d states as a result of their orbital-selective quantization.