Strong-Pinning Effects in Low-Temperature Creep: Charge-Density Waves in   TaS_3
  Nonlinear conduction in the quasi-one dimensional conductor o-TaS_3 has been studied in the low-temperature region down to 30 mK. It was found that at temperatures below a few Kelvins the current-voltage (I-V) characteristics consist of several branches. The temperature evolution of the I-V curve proceeds through sequential freezing-out of the branches. The origin of each branch is attributed to a particular strong pinning impurity type.   Similar behavior is expected for other physical systems with collective transport (spin-density waves, Wigner crystals, vortex lattices in type-II superconductors etc.) in the presence of strong pinning centers. 
S.V. Zaitsev-Zotov (IRE RAS, Moscow, Russia), G. Remenyi and P.   Monceau (CNRS-CRTBT Grenoble, France)