Optical investigations onY2−xBixRu2O7: Electro

Abstract

Optical conductivity spectra of cubic pyrochlore Y2−xBixRu2O7 (0.0≤x≤2.0) compounds are investigated. As a metal-insulator transition (MIT) occurs around x=0.8, large spectral changes are observed. With increase of x, the correlation-induced peak between the lower and the upper Hubbard bands seems to be suppressed, and a strong mid-infrared feature is observed. In addition, the p − d charge transfer peak shifts to the lower energies. The spectral changes cannot be explained by electronic structural evolutions in the simple bandwidth-controlled MIT picture, but are consistent with those in the filling-controlled MIT picture. In addition, they are also similar to the spectral changes of Y2−xCaxRu2O7 compounds, which is a typical filling-controlled system. This work suggests that, near the MIT, the Ru bands could be doped with the easily polarizable Bi cations.

Infrared study of the electronic structure of the metallic pyrochlore iridate Bi2Ir2O7

“…Bi-related pyrochlore (Bi,Y) 2 Ru 2 O 7 , and was attributed to the mid-gap state formed by the effective doping of the Bi bands near the Fermi level [46]. The mid-gap state has been found in some doped Mott/charge-transfer insulators with large bandgaps, which is not the case of our iridate pyrochlore.…”

Self-doping induced orbital-selective Mott transition inHg2Ru2O7

“…Namely, a negative chargetransfer associated self-doping drives an orbital-selective MIT at low temperatures via the Mott-Hubbard route. Our study should be more generally applicable to MO pyrochlore systems, and, in particular, to Tl 2 Mn 2 O 7 , exhibiting Mott-Hubbard transitions 14,21,24,29 as functions of suitable "tuning parameters".…”

Evidence of a correlation between magnetic and structural transitions in Y2−xZnxRu2O7 pyrochlore compounds

“…Chemical doping at the A site with divalent cations would also imply a hole doping effect, expectedly providing these systems with the electronic conductivity required to overcome the Mott-Hubbard threshold. 13 This effect, coupled with ionic conductivity due to vacancy disorder, makes doped Y 2 Ru 2 O 7 even more prospective cathode materials for IT-SOFC. 14 Moreover in pyrochlores, cation or anion disorder may give rise to order-disorder transitions inuencing also the conductivity and the presence of metal-insulator transitions.…”