Investigations of the breakdown transition, hysteresis, and periodic-pulse oscillation in Tl/W-doped blue bronzes

Nonlinear transport behavior, which shows a sudden breakdown transition to zero- or negative-differential resistance in the high field, is observed in the quenched thallium- or tungsten-doped blue bronzes K0.15Tl0.15MoO3 and Tl0.3Mo1-xWxO3 at 77 K. It is found that the critical breakdown transition threshold is unstable for the induced field and decreases with increasing cycling times of the conducting current and, finally, reaches a definite value. When the current increases from 30 to 100 mA, the voltage between the two ends of the sample does not show a clear increase, i.e., a similar phenomenon with zero-differential resistance. On the downward cycle of the current, the voltage-current curve exhibits a large electronic hysteresis over the nonlinear region. On the other hand, in the critical region, the breakdown transition is usually accompanied by a voltage pulse with a large amplitude and exhibits a negative-differential resistance. These effects of an electric field on a pinned charge-density wave are phenomenologically interpreted in analogy with the mechanical deformations of the crystal solid.