Observation of correlations up to the micrometer scale in sliding charge-density waves

TL;DR

This study uses high-resolution x-ray diffraction to reveal super long-range electronic correlations in a charge density wave system, showing correlations up to micrometer scales during sliding regimes.

Contribution

It provides the first direct measurement of super long-range correlations in charge density waves using coherent x-ray diffraction.

Findings

Correlations extend up to micrometer scale, much larger than the CDW period.

Secondary satellites indicate super long-range order during sliding.

Correlations are inherent to the collective electron dynamics in CDWs.

Abstract

High-resolution coherent x-ray diffraction experiment has been performed on the charge density wave (CDW) system K$_{0.3}$MoO$_3$. The $2k_F$ satellite reflection associated with the CDW has been measured with respect to external dc currents. In the sliding regime, the $2k_F$ satellite reflection displays secondary satellites along the chain axis which corresponds to correlations up to the micrometer scale. This super long range order is 1500 times larger than the CDW period itself. This new type of electronic correlation seems inherent to the collective dynamics of electrons in charge density wave systems. Several scenarios are discussed.