Distinct fingerprints of charge density waves and electronic standing waves in ZrTe$_3$

TL;DR

This study uses resonant X-ray diffraction to distinguish charge density waves from electronic standing waves in ZrTe$_3$, revealing that CDWs emerge from a uniform electronic fluid influenced by Friedel oscillations, with distinct signatures and dynamics.

Contribution

It demonstrates a method to differentiate charge density waves from Friedel oscillations in ZrTe$_3$ through experimental signatures and correlation length analysis.

Findings

Two independent diffraction signatures near the CDW transition.

Distinct correlation lengths develop in the well-ordered state.

Anomalously slow dynamics of mesoscopic nanoregions observed.

Abstract

Experimental signatures of charge density waves (CDW) in high-temperature superconductors have evoked much recent interest, yet an alternative interpretation has been theoretically raised based on electronic standing waves resulting from quasiparticles scattering off impurities or defects, also known as Friedel oscillations (FO). Indeed the two phenomena are similar and related, posing a challenge to their experimental differentiation. Here we report a resonant X-ray diffraction study of ZrTe$_3$, a model CDW material. Near the CDW transition, we observe two independent diffraction signatures that arise concomitantly, only to become clearly separated in momentum while developing very different correlation lengths in the well-ordered state. Anomalously slow dynamics of mesoscopic ordered nanoregions are further found near the transition temperature, in spite of the expected strong thermal fluctuations. These observations reveal that a spatially-modulated CDW phase emerges out of a uniform electronic fluid via a process that is promoted by self-amplifying FO, and identify a viable experimental route to distinguish CDW and FO.