Fermi surface topology in a metallic phase of VO2 thin films grown on TiO2(001) substrates

Since the first observation of the metal-to-insulator transition (MIT), VO2 has attracted substantial attention in terms of whether this transition is impelled by electronphonon interaction (Peierls transition) or electronelectron interaction. Regarding Peierls transition, it has been theoretically predicted that the Fermi surface (FS) cross-section exhibits certain nesting features for a metallic phase of VO2. Various experimental studies related to the nesting feature have been reported. Nevertheless, there is no experimental result on FS topology. In this work, we determine the FS topology of the metallic phase of VO2 through studies of VO2 epitaxial thin films on TiO2(001) substrates, using synchrotron radiation angle-resolved photoemission spectroscopy (ARPES). Three electron pockets around Gamma are observed in band structures along the Gamma X direction. These three bands form electron surfaces around Gamma in the GXRZ plane. Furthermore, the lowest energy band FS exhibits the nesting feature corresponding to a nesting vector (q) over right arrow=Gamma R, as predicted by the calculation. Our results strongly indicate the formation of the charge-density wave with (q) over right arrow=Gamma R and thus, the importance of Peierls transition for the mechanism of the MIT in VO2.