Angle-resolved photoemission study of the mixed valence oxide V₆O₁₃: Quasi-one-dimensional electronic structure and its change across the metal-insulator transition

We have performed angle-resolved photoemission spectroscopy of mixed valence oxide V₆O₁₃ that shows a metal-insulator transition (MIT) at ≃ 150 K. In the metallic phase, we observe two bands near the Fermi level (E_F). One is a prominent band located around 0.8 eV and the other is a weak structure around 0.2 eV that shows dispersion toward E_F only along the b axis. Furthermore, though the momentum distribution curve at E_F shows a peak at kb/π=0.29±0.01 indicative of a E_F crossing, the intensity of the band near E_F is strongly suppressed in the region of E_F. These observations indicate quasi-one-dimensional electronic states of V₆O₁₃, consistent with a highly anisotropic behavior observed from resistivity and optical conductivity measurements. Across the MIT, the band near E_F shifts to higher binding energy and becomes less dispersive, resulting in opening of an energy gap of 0.2 eV. We discuss some implications of the experimental results.