Phase diagram and optical conductivity of La1.8 xEu0.2SrxCuO4

The optical properties of a V4O7 single crystal have been investigated from the high temperature metallic phase down to the low temperature antiferromagnetic insulating phase. The temperature dependent behavior of the optical conductivity across the metal to insulator MIT transition can be explained in a polaronic scenario. Charge carriers form strongly localized polarons in the insulating phase, as suggested by a far infrared charge gap abruptly opening at TMIT amp; 8776; 237 K. In the metallic phase, instead, the presence of a Drude term is indicative of fairly delocalized charges with a moderately renormalized mass m amp; 8727; amp; 8776; 5me. The electronic spectral weight is almost recovered on an energy scale of 1 eV, which is much narrower than in the VO2 and V2O3 cases. Those findings suggest that electron lattice interaction rather than electronic correlation is the driving force for the V4O7 metal insulator transitio