Depinning of charge density waves of different dimensionalities in 1T-TiSe₂and NbSe₃

Nonlinear transport behavior is one of the signatures of the formation of electronic crystals such as charge density wave (CDW), as it provides evidence for their collective motion. Such experimental evidence has been widely reported in quasi-one-dimensional (1D) materials but is rarely studied in 2D systems. Only a few studies on the RTe₃materials have been previsouly reported. Here we report for the first time the observation of CDW depinning and sliding in the layered 1T-TiSe₂compound, based on the observation of (1) nonlinear voltage-current characteristics and (2) the electrical noise, which are associated with the CDW depinning and sliding process. Similar measurements are also conducted on quasi-1D system NbSe₃. The depinning behavior of the CDWs with different dimensionalities in these two systems are compared. It is found that the threshold electric field (E) increases linearly with decreasing temperature for the 2D case, consistent with previous results on RTe₃, while it demonstrated an activated behavior in 1D, as expected within the weak-pinning Fukuyama-Lee-Rice framework. Such a distinction of the threshold behavior in CDW systems of different dimensions therefore indicates a possible strong pinning picture in higher-dimensional CDW systems in general.Eis found to be much higher in 1T-TiSe₂, consistent with a strong pinning picture, and could account for the scarcity of the depinning study in these 2D systems. Our results thus pave the way for a unified understanding of the CDW collective motion in different dimensionalities.