Temperature-dependent self-doping effects on the metal-insulator transition of Tl2Ru2O7 - art. no. 165108

We investigated temperature (T-) dependent optical conductivity spectra for Tl2Ru2O7, which shows a metal-insulator (MI) transition at T(MI)similar to 125 K. It was found that there is a strong mid-infrared peak and that its T-dependent spectral weight changes are quite significant. In particular, i ts T dependences are similar to the doping dependences of the mid-infrared peak in an externally doped Mott insulator. These intriguing phenomena can be explained by self-doping for the Ru 4d states in the presence of an easi ly polarizable Tl cation. Moreover, the T-dependent amount of self-doping i s found to be closely related to the MI transition.