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 A1g electrons is superimposed on the isotropic hopping conduction of localized Eg electrons. The "bad-metal" character and the weak anisotropy are the consequences of the large effective mass meff >7me and scattering rate Γ 160meV of the quasiparticles in the A1g band. There is a pseudogap above TMI=69K, and in the insulating phase the gap follows the BCS-like temperature dependence of the structural order parameter with Δch >42meV in the ground state. The MIT is described in terms of a weakly coupled two-band model.