Journal of superconductivity vol:15 issue:5 pages:495-498
date:Katholieke Univ Leuven, Vaste Stof Fys Magnetisme Lab, B-3001 Louvain, Belgium; Univ Groningen, Solid State Phys Lab, NL-9747 AG Groningen, Netherlands; Inst Phys, Belgrade 11080, Yugoslavia; Univ Tokyo, Inst Solid State Phys, Chiba 2778581, Japan
The optical properties of sodium-deficient alpha'-NaxV2O5 (0.85 less than or equal to x less than or equal to 1.00) single crystals are analyzed using ellipsometry, and infrared reflectivity techniques. In sodium deficient samples, the optical absorption peak associated to the fundamental electronic gap develops in the middle of the pure alpha'-NaV2O5 gap at similar to0.44 eV, and the material remains insulating up to the maximal achieved hole concentration of about 15%. Nonmetallic behavior under hole doping provoked reinterpretation of the alpha'-NaV2O5 optical spectra. We argue that the absorption peak at about 0.9 eV corresponds to the photoionization energy of a large polaron.