X-Ray Diffraction from Pinned Charge Density Waves

TL;DR

This paper uses x-ray diffraction to investigate how impurities affect charge density waves in doped materials, revealing interference effects, asymmetries, and Friedel oscillations around defects.

Contribution

It provides the first direct x-ray evidence of Friedel oscillations around impurities in doped charge density wave systems.

Findings

Asymmetry between +2k_f and -2k_f satellite reflections observed.

Friedel oscillations detected around impurity atoms.

Impurity pinning influences charge density wave profiles.

Abstract

We present an x-ray study of doped charge density waves systems. When a 2k_f-charge density wave is strongly pinned to impurities, an interference effect gives rise to an asymmetry between the intensities of the +2k_f and -2k_f satellite reflections. Moreover, profile asymmetry of the satellite reflections indicates the existence of Friedel oscillations (FOs) around the defects. We have studied these effects in V- and W-doped blue bronzes. A syncrotron radiation study of the V-doped blue bronze clearly reveals the presence of FO around the V atoms.