Angle-resolved photoemission study of the mixed valence oxideV6O13:Quasi-one-dimensional electronic structure and its change across the metal-insulator transition

Abstract

We have performed angle-resolved photoemission spectroscopy of mixed valence oxide ${\mathrm{V}}_{6}{\mathrm{O}}_{13}$ that shows a metal-insulator transition (MIT) at $\ensuremath{\simeq}150 \mathrm{K}.$ 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 $kb/\ensuremath{\pi}=0.29\ifmmode\pm\else\textpm\fi{}0.01$ 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 ${\mathrm{V}}_{6}{\mathrm{O}}_{13},$ 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.