Dynamic electron correlations with charge order wavelength along all directions in the copper oxide plane

TL;DR

This study uses resonant x-ray scattering to reveal dynamic charge order fluctuations in cuprate superconductors, showing a quasi-circular pattern indicating competing phases and symmetry breaking driven by Coulomb interactions.

Contribution

It demonstrates the existence of a dynamic, quasi-circular charge order pattern in cuprates, linking short-range fluctuations to Coulomb interactions and symmetry breaking.

Findings

Discovery of a quasi-circular charge order pattern.

Charge domains can dynamically rotate in the CuO2 plane.

Evidence of Brazovskii-type fluctuations in cuprates.

Abstract

In strongly correlated systems the strength of Coulomb interactions between electrons, relative to their kinetic energy, plays a central role in determining their emergent quantum mechanical phases. We perform resonant x-ray scattering on Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, a prototypical cuprate superconductor, to probe electronic correlations within the CuO$_2$ plane. We discover a dynamic quasi-circular pattern in the $x$-$y$ scattering plane with a radius that matches the wave vector magnitude of the well-known static charge order. Along with doping- and temperature-dependent measurements, our experiments reveal a picture of charge order competing with superconductivity where short-range domains along $x$ and $y$ can dynamically rotate into any other in-plane direction. This quasi-circular spectrum, a hallmark of Brazovskii-type fluctuations, has immediate consequences to our understanding of rotational and translational symmetry breaking in the cuprates. We discuss how the combination of short- and long-range Coulomb interactions results in an effective non-monotonic potential that may determine the quasi-circular pattern.