DEPINNING OF THE CHARGE-DENSITY WAVE IN PURE AND NONSTOICHIOMETRIC BLUE BRONZES A0.30MOO3 (A=K, RB)

We report the observation of non-linear voltage response to unipolar current pulses in pure A0.30MoO3 (A = K, Rb) and non-stoichiometric Rb0.28MoO3 blue bronzes near threshold for depinning of the charge density wave. In both types of samples, the transient response waveforms involve overshoot at the leading edge and a tail at the trailing edge of the pulse whose time decays obey stretched exponential laws exp-(t/-tau)beta (0 < beta < 1). The characteristic times are found to be approximately one order of magnitude larger in Rb0.28MoO3 than in pure samples. The results are discussed in terms of charge density wave phase dislocations coupled to point lattice defects.