Charge Correlations in Cuprate Superconductors

High-temperature superconductivity, with transition temperatures up to approximate to 134Kat ambient pressure, occurs in layered cuprate compounds.The conducting CuO2 planes, which are universally present, are responsible for the superconductivity but also show a disposition to other competing states including spin and charge order. Charge-density-wave (CDW) order appears to be a universal property of cuprate superconductors. It has been studied via a multitude of probes including X-ray and neutron scattering, nuclear magnetic resonance, scanning probe techniques, electronic transport, and quantum oscillations. Here, we review the microscopic properties of the CDWorder.We discuss the nature of the ordered state, that is, its symmetry and microscopic structure. Furthermore, we show how the CDWorder is related to quenched disorder, host structure, symmetry breaking perturbations, and magnetic fields. We also describe measurements of dynamic collective charge excitations that are closely related to the quasi-static CDW order. Finally, we highlight some of the debated issues in the field, including the origin of the CDWorder, the relationship to spin order, and the nature of the spatial CDWcorrelations.