Separation of orbital contributions to the optical conductivity of BaVS3

The correlation-driven metal-insulator transition (MIT) of BaVS3 was studied by polarized infrared spectroscopy. In the metallic state two types of electrons coexist at the Fermi energy: The quasi-1D metallic transport of A(1g) electrons is superimposed on the isotropic hopping conduction of localized E-g electrons. The "bad-metal" character and the weak anisotropy are the consequences of the large effective mass m(eff)approximate to 7m(e) and scattering rate Gamma >= 160 meV of the quasiparticles in the A(1g) band. There is a pseudogap above T-MI=69 K, and in the insulating phase the gap follows the BCS-like temperature dependence of the structural order parameter with Delta(ch)approximate to 42 meV in the ground state. The MIT is described in terms of a weakly coupled two-band model.