Polarized reflectance measurements of the CDW transitions in h-Mo4O11 and g-Mo4O11

Temperature-dependent ~300–10 K! reflectance measurements were made on h-Mo4O11 and g-Mo4O11 in the conducting b-c plane in the frequency range 30–8000 cm, for light polarized both parallel and perpendicular to the charge density wave ~CDW! direction ~b axis!. The optical conductivity was determined from a Kramers-Kronig analysis of the reflectance. The data clearly show strong suppression of the conductivity in the c-axis direction below the CDW transition temperatures, leading to a partial optical gap in the spectrum. The b-axis conductivity does not show as strong a suppression except at low frequencies. The CDW gap energies for both crystals are evaluated, in agreement with those obtained from transport data. The data are considered in light of recent work on stripes and charge ordering in the field of superconductivity. @S0163-1829~98!05644-6#