Charge density wave transport in NbSe$_3$ at low temperatures under high magnetic field

Charge density wave (CDW) depinning and sliding regimes have been studied in NbSe$_3$ at low temperatures down to 1.5 K under magnetic field of 19 T oriented along the $c$-axis. We found that the threshold field for CDW depinning becomes temperature independent below $T_0\approx15\,$K. Also CDW current to frequency ratio characterizing CDW sliding regime increases by factor 1.7 below this temperature. The results are discussed as a crossover from thermal fluctuation to tunneling CDW depinning at $T<T_0$. Besides, we found that CDW sliding strongly suppresses the amplitude of Shubnikov-de Haas oscillations of magnetoresistance.