Contact and bulk electromodulated transmission spectra of blue bronze

Abstract
We have used electromodulated infrared transmission spectroscopy to search for states associated with soliton excitations of the CDW phase in blue bronze with tunable diode lasers. In particular, we have searched the spectral region near the edge of the CDW gap and compared the spectra associated with contact polarization (i.e. current injection) with that associated with bulk CDW polarization. No new states are observed, implying that the lifetime of injected solitons is < 0.5 µs. Both bulk and contact polarization are observed to shift the frequency of high energy phonons, suggesting that the density of electronic states in the gap, present because of CDW fluctuations, depends on CDW polarization.