Spectral weight transfer in strongly correlated Fe_1.03Te

The temperature dependence of the in-plane optical conductivity has been determined for Fe_1.03Te above and below the magnetic and structural transition at TN≃68 K. The electron and hole pockets are treated as two separate electronic subsystems: a strong, broad Drude response that is largely temperature independent, and a much weaker, narrow Drude response with a strong temperature dependence. Spectral weight is transferred from high to low frequency below TN, resulting in the dramatic increase of both the low-frequency conductivity and the related plasma frequency. The change in the plasma frequency is due to an increase in the carrier concentration resulting from the closing of the pseudogap on the electron pocket, as well as the likely decrease of the effective mass in the antiferromagnetic state.