Abstract
Infrared optical investigations of have been performed in the spectral range from 80 to down to temperatures as low as 10 K by applying hydrostatic pressure. In the metallic state, K, we observe a 50% increase in the Drude contribution as well as the mid-infrared band due to the growing intermolecular orbital overlap with pressure up to 11 kbar. In the ordered state, , we extract how the electronic charge per molecule varies with temperature and pressure: Transport and optical studies demonstrate that charge order and metal-insulator transition coincide and consistently yield a linear decrease of the transition temperature by K/kbar. The charge disproportionation diminishes by /kbar and the optical gap between the bands decreases with pressure by /kbar. In our high-pressure and low-temperature experiments, we do observe contributions from the massive charge carriers as well as from massless electrons to the low-frequency optical conductivity, however, without being able to disentangle them unambiguously.
10 More- Received 18 January 2016
- Revised 22 April 2016
DOI:https://doi.org/10.1103/PhysRevB.93.195116
©2016 American Physical Society