We studied the physical properties of hollandite titanates, BaxTi8O16+δ, which have double chains of edge-sharing TiO6 octahedra with d electrons in the t2g states. We found that there is an electronic phase transition at ∼220 K, at which various properties exhibit anomalies. This phase transition is characterized by a modulation in the TiO6 chains and a spectral weight transfer of over 2 eV in the optical conductivity spectrum, which are presumably caused by charge and orbital ordering of the Ti t2g electrons.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 2015 Dec 14