Abstract
The optical properties of a 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 237 K. In the metallic phase, instead, the presence of a Drude term is indicative of fairly delocalized charges with a moderately renormalized mass . The electronic spectral weight is almost recovered on an energy scale of 1 eV, which is much narrower than in the and cases. Those findings suggest that electron-lattice interaction rather than electronic correlation is the driving force for the metal-insulator transition.
- Received 1 July 2014
- Revised 4 September 2014
DOI:https://doi.org/10.1103/PhysRevB.90.115149
©2014 American Physical Society