Theory of plastic flows of CDWs in application to a current conversion

We suggest a theoretical picture for distributions of plastic deformations experienced by a sliding Charge Density Wave in the course of the conversion from the normal current at the contact to the collective one in the bulk. Several mechanisms of phase slips via creation and proliferation of dislocations are compared. The results are applied to space resolved X-ray [1,2], multi-contact [3,4] and optical [5] studies. Numerical simulations are combined with model independent relations. 1. INTRODUCTION. Plastic deformations and flows are currently the focus of studies of Electronic Crystals (charge/spin density waves(DW) and interface 2d Wigner crystals) and of vortex lattices. Thus, dislocations are supposed to participate in depinning, in phase slips, in narrow band noise generation, and also arise in contact structures. Experimental studies show that the sliding state of DWs is essentially inhomo-geneous [1-6] with different effects near contacts and in the bulk. We present general scheme to describe inhomogeneous distributions of deformations (which are the gradients ϕ ′ = q along the chain axe x of the phase ϕ), electric fields and currents in the course of the current conversion. For a long enough sample we predict a strong variation for the shift q(x) of the CDW wave number near contacts which flattens (nearly exponentially) towards the bulk, δx → ∞.The bulk strain like q = q