Variable-temperature infrared spectroscopic study of some molybdenum bronzes: evidence for electron–phonon coupling

Abstract

An infrared vibrational spectroscopic study of some molybdenum oxide bronzes, commonly termed the ‘blue’ bronzes, the ‘red’ bronzes and the ‘purple’ bronzes has been made. The charge density wave driven metal-to-semiconducting phase transition, mediated through electron–phonon coupling, is evidence in the infrared spectra of the blue bronze studied as anomalous intensity behaviour on some of the internal modes, specifically in the lower-frequency Mo—O—Mo stretching region. Significant intensity differences are observed between these different classes of bronzes: a qualitative explanation for these differences is given.