The temperature (T) dependent metal-insulator transition (MIT) in VO2​ is
investigated using bulk sensitive hard x-ray (∼ 8 keV) valence band, core
level, and V 2p−3d resonant photoemission spectroscopy (PES). The valence
band and core level spectra are compared with full-multiplet cluster model
calculations including a coherent screening channel. Across the MIT, V 3d
spectral weight transfer from the coherent (d1C​ final)
states at Fermi level to the incoherent (d0+d1L​ final)
states, corresponding to the lower Hubbard band, lead to gap-formation. The
spectral shape changes in V 1s and V 2p core levels as well as the valence
band are nicely reproduced from a cluster model calculations, providing
electronic structure parameters. Resonant-PES finds that the
d1L​ states resonate across the V 2p−3d threshold in
addition to the d0 and d1C​ states. The results support
a Mott-Hubbard transition picture for the first order MIT in VO2​.Comment: 6 pages, 3 figures. to be published in Phys. Rev.