Charge and Sodium Ordering in β-Na0.33V2O3

The recent discovery [1] of a clear metal– insulator transition (MIT) in the vanadium bronze βNa0.33V2O3 has sparked a revival of interest in this quasi one-dimensional(1D) metallic system. In addition to the MIT, β-Na0.33V2O3 undergoes a structural sodium ordering transition at higher temperatures, a magnetic transition at low temperatures, and a transition into a superconducting state under high pressure [2]. Several important aspects of this 1D material have remained unclear, including the nature of the spin and charge excitations, and the relation between the Na ordering and the MIT. This contribution presents a Raman and optical study of β-Na0.33V2O3 focusing on the various phase transitions and electron–phonon coupling in this compound.