Low-dimensional chaos and high-dimensional behavior in the switching charge-density-wave conductor NbSe₃

We study the dynamics of the switching charge-density-wave (CDW) conductor NbSe₃ in the presence of combined dc and ac electric fields. At a driving frequency of 20 MHz, the dynamics are both low-dimensional and chaotic, while at lower drive frequencies (<5 MHz) high-dimensional dynamics are observed. Analysis of the time series provides Lyapunov exponents, and an estimate for the number of active degrees of freedom for the low-dimensional chaotic behavior. The principal nonlinearity which gives rise to the low-dimensional chaos in switching CDW’s is shown to be the hysteresis in the depinning transition, rather than the interaction between two frequencies.