Electromodulated infrared transmission spectra of blue bronze

The infrared transmission of the quasi-one dimensional charge-density-wave (CDW) conductor blue bronze (K0.3MoO3) is affected by polarization of the C DW, and therefore by application of a voltage near or above the threshold f or CDW depinning. In this paper, we compare the spectra associated with the relative change in transmission (Delta tau/tau) taken for different temper atures and oscillating voltages. We find that the phonon spectrum is affect ed by CDW polarization; the linewidths or frequencies of most phonons chang e by approximate to 0.01 cm(-1). However, no new intragap states that can b e associated with current injection are observed; i.e. the spectra associat ed with polarization of the CDW in the crystal bulk is identical to that as sociated with CDW current injection near the contacts. Our results indicate that, for light polarized perpendicular to the conducting chains, the dens ity (n), cross-section (sigma), and bandwidth (Gamma) of intragap states ar e related by: n sigma/Gamma < 10(-10) (A cm(-1))(-1). For expected values o f the cross-section and bandwidth, this implies that the intragap states ca n be optically excited for a time less than 0.3 mu s.