Electronic structure of metallic K0.3MoO3 and insulating MoO3 from high-energy spectroscopy

We present high-energy spectroscopy results on the occupied and unoccupied electronic structures of the strongly anisotropic compounds MoO3 and K0.3Mo O3 near the Fermi level. X-ray photoemission reveals a close similarity of the valence-band spectra in both materials. The metal K0.3MoO3 shows an add itional Mo 4d-derived conduction band whose population is achieved by elect ron transfer from K to Mo. This is concluded from studies on intentional su rface doping of insulating MoO3 which leads to the occurrence of Mo 4d-like defect states near the Fermi level. Information on the unoccupied states a nd their orbital symmetries was obtained by polarization-dependent x-ray ab sorption spectroscopy. These experiments confirm previous descriptions of t he electronic structure in terms of a molecular-orbital picture. For K0.3Mo O3, strong local Mo 4d-O 2p bonding is not only found along the chain direc tion but also perpendicular to it. This finding is reminiscent of earlier b and calculations, which found the chains to form pairs by pronounced transv erse hybridization, with the overall bandwidth remaining one dimensionally anisotropic. This adds an important aspect to the discussion on possible Lu ttinger-liquid physics in the low-dimensional Mo bronzes. [S0163-1829(99)02 636-3].