  Oxygen vacancies created in anatase TiO2 by UV photons (80 - 130 eV) provide
an effective electron-doping mechanism and induce a hitherto unobserved
dispersive metallic state. Angle resolved photoemission (ARPES) reveals that
the quasiparticles are large polarons. These results indicate that anatase can
be tuned from an insulator to a polaron gas to a weakly correlated metal as a
function of doping and clarify the nature of conductivity in this material.
