Charge and Spin Density Waves observed through their spatial fluctuations by coherent and simultaneous X-ray diffraction

TL;DR

This study uses advanced X-ray diffraction to compare spatial fluctuations of charge and spin density waves in chromium, revealing distinct behaviors that challenge traditional magneto-elastic theories and support an electronic origin of the charge density wave.

Contribution

It provides the first direct comparison of spatial fluctuations of SDW and CDW in chromium, showing their different behaviors and supporting a purely electronic model for CDW formation.

Findings

Charge density wave exhibits speckles indicating short-range order.

Spin density wave maintains long-range order with minimal fluctuations.

Results support a second harmonic electronic scenario for CDW in chromium.

Abstract

Spatial uctuations of spin density wave (SDW) and charge density wave (CDW) in chromium have been compared by combining coherent and simultaneous X-ray diffraction experiments. Despite their close relationship, spatial fluctuations of the spin and of the charge density waves display a very different behavior: the satellite reflection associated to the charge density displays speckles while the spin one displays an impressive long-range order. This observation is hardly compatible with the commonly accepted magneto-elastic origin of CDW in chromium and is more consistent with a purely electronic scenario where CDW is the second harmonic of SDW. A BCS model taking into account a second order nesting predicts correctly the existence of a CDW and explains why the CDW is more sensitive to punctual defects.