Electro-reflectance spectra of blue bronze

We show that the infrared reflectance of the quasi-one dimensional charge-density-wave (CDW) conductor K_0.3MoO₃ (blue bronze) varies with position when a voltage greater than the CDW depinning threshold is applied. The spatial dependence and spectra associated with these changes are generally as expected from the electro-transmission [B.M. Emerling, et al., Eur. Phys. J. B 16, 295 (2000)], but there are differences which might be associated with changes in the CDW properties on the surface. We have examined the electro-reflectance spectrum associated with CDW current investigation for light polarized parallel to the conducting chains for signs of expected current-induced intragap states, and conclude that the density of any such states is at least an order of magnitude less than expected.