Tracking defects of Electronic Crystals by Coherent X-ray Diffraction

TL;DR

This review discusses how advanced coherent x-ray diffraction techniques reveal the behavior of charge and spin density wave systems, especially their phase dynamics, sliding states, and defect propagation, providing new insights into symmetry-breaking phenomena.

Contribution

It introduces the application of coherent x-ray diffraction to study CDW and SDW systems, highlighting novel observations of sliding states, surface pinning effects, and phase defect propagation.

Findings

Detection of phase fluctuations in sliding CDWs

Observation of surface pinning effects

Propagation of charge solitons across samples

Abstract

In this article, we review different studies based on advanced x-ray diffraction techniques - especially coherent x-ray diffraction - that allowed us to reveal the behaviour of such symmetry-breaking systems as Charge Density Wave (CDW) and Spin density Wave (SDW), through their local phase. After a brief introduction on the added value of using coherent x-rays, we show how the method can be applied to CDW and SDW systems, in both static and dynamical regimes. The approach allowed us to probe the particular sliding state of CDWs systems by observing them through their phase fluctuations, to which coherent x-rays are particularly sensitive. Several compounds stabilizing a CDW phase able to slide are presented, each with a different but clearly pronounced signature of the sliding state. Two main features emerge from this series of experiments which have been little treated until now, the influence of CDW pinning by the sample surfaces and the propagation of periodic phase defects such as charge solitons across the entire sample. Phase models describing the spatial and temporal properties of sliding CDWs are presented in the last part of this review.