Hall effect in the pinned and sliding charge density wave state of NbSe3

Results of Hall effect measurements are reported both below and above the threshold electric field, E-t, for depinning the low temperature charge density wave (CDW) in NbSe3 in a wide temperature range. At low electric fields, below E-t, we have observed a change in the sign of the Hall voltage at all temperatures lower than T-p2. Comparison between the Hall effect and the magnetoresistance behavior indicates that the n-type conductivity in the low magnetic field range differs qualitatively from the p-type conductivity in the high field range. We demonstrate that at low temperature the CDW motion significantly alters the Hall voltage. These results indicate that, in NbSe3, the CDW in the sliding state interacts essentially with holes. Possible mechanisms of this effect are discussed.