Abstract
We present a polarization-dependent infrared reflectivity study of the spin-ladder compound under pressure. The optical response is strongly anisotropic, with the highest reflectivity along the ladders/chains revealing a metallic character. For the polarization direction perpendicular to the ladder plane, an insulating behavior is observed. With increasing pressure the optical conductivity for shows a strong increase, which is most pronounced below . According to the spectral weight analysis of the optical conductivity the hole concentration in the ladders increases with increasing pressure and tends to saturate at high pressure. At GPa the number of holes per Cu atom in the ladders has increased by , and the Cu valence in the ladders has reached the value . The optical data suggest that remains electronically highly anisotropic up to high pressure, also at low temperatures.
2 More- Received 3 November 2014
- Revised 27 November 2014
DOI:https://doi.org/10.1103/PhysRevB.90.224516
©2014 American Physical Society