Macroscopic quantum tunneling of charge density waves

We study the quantum tunneling of CDW theoretically based on the extended F ukuyama-Lee-Rice model in which the vortex excitation is allowed. By consid ering both bulk and edge processes we can explain the experimental results of the I-V characteristic and the condition for the observation of the tunn eling current. We also study the classical depinning problem of commensurat e CDW interacting with an impurity. It turns out that the: impurity can ass ist the depinning, that is, the threshold field in the presence of impurity can be lower than that in its absence.