# Theory of charge density wave depinning by electromechanical effect

## TL;DR

This paper introduces the first theoretical model explaining how charge density waves (CDWs) depin under electric fields through an electromechanical mechanism involving a local field effect, linking dielectric properties to CDW mobility.

## Contribution

It presents a novel theory for CDW depinning based on electromechanical effects and local field interactions, applicable to low-dimensional incommensurate CDWs in the strong electron-phonon regime.

## Key findings

- Finite threshold electric field causes CDW depinning.
- Discontinuities in modulation functions vanish at depinning.
- Depinning transition observable via phonon spectrum changes.

## Abstract

We discuss the first theory for the depinning of low dimensional, incommensurate, charge density waves (CDWs) in the strong electron-phonon (e-p) regime. Arguing that most real CDWs systems invariably develop a gigantic dielectric constant (GDC) at very low frequencies, we propose an electromechanical mechanism which is based on a local field effect. At zero electric field and large enough e-p coupling the structures are naturally pinned by the lattice due to its discreteness, and develop modulation functions which are characterized by discontinuities. When the electric field is turned on, we show that it exists a finite threshold value for the electric field above which the discontinuities of the modulation functions vanish due to CDW deformation. The CDW is then free to move. The signature of this pinning/depinning transition as a function of the increasing electric field can be directly observed in the phonon spectrum by using inelastic neutrons or X-rays experiments.