Precision measurement of charge-order formation by coherent Resonant X-ray Scattering

We report experimental research on the spontaneous formation of charge order and its relationship with disorder pinning effects. By studying a prototypical charge-density-wave material, ZrTe₃, with high-precision resonant elastic X-ray scattering (REXS), we observe a clear temperature evolution of the ordering wave vector, along with a drastic increase in the correlation length, upon the development of the long-range charge order below T ≈ 63 K. These results are attributed to band-structure changes near the Fermi level due to the opening of the charge-ordering gap. By further utilizing a coherent X-ray beam, we are able to reveal unprecedented details in the mesoscopic dynamics of the charge order by X-ray photon correlation spectroscopy (XPCS), the results of which can be most naturally explained by the combined effects of thermal activation and disorder pinning. Our results provide empirical insights for understanding charge-order phenomena in correlated-electron systems such as the high-Tc cuprates.