Impurity effects on quantum depinning of commensurate charge density waves

We investigate quantum depinning of the one-dimensional (1D) commensurate c harge-density wave (CDW) in the presence of one impurity theoretically. Qua ntum tunneling rate below but close to the threshold field is calculated at absolute zero temperature by use of the phase Hamiltonian within the WKB a pproximation. We show that the impurity can induce localized fluctuation an d enhance the quantum depinning. The electric field dependence of the tunne ling rate in the presence of the impurity is different from that in its abs ence.