Aubry transition with small distortions

TL;DR

This paper demonstrates that the Aubry transition can occur with small distortions in incommensurately distorted structures by modifying the potential shape, explaining experimentally observed pinned phases with minimal distortions.

Contribution

It introduces a modified potential model showing the Aubry transition at small distortion amplitudes, contrasting with the standard model.

Findings

A small distortion amplitude can induce the Aubry transition.

A phason gap opens at the transition point.

The phonon spectrum remains similar to the undistorted case at higher energies.

Abstract

We show that when the Aubry transition occurs in incommensurately distorted structures, the amplitude of the distortions is not necessarily large as suggested by the standard Frenkel-Kontorova mechanical model. By modifying the shape of the potential in such a way that the mechanical force is locally stronger (i.e. increasing the nonlinearities), the transition may occur at a small amplitude of the potential with small distortions. A "phason" gap then opens, while the phonon spectrum resembles a standard undistorted spectrum at higher energies. This may explain the existence of pinned phases with small distortions as experimentally observed in charge-density waves.