In high-TC​ cuprates, superconductivity and charge density waves (CDW)
are competitive, yet coexisting orders. To understand their microscopic
interdependence a probe capable of discerning their interaction on its natural
length and time scales is necessary. Here we use ultrafast resonant soft x-ray
scattering to track the transient evolution of CDW correlations in
YBa2​Cu3​O6+x​ following the quench of superconductivity by an
infrared laser pulse. We observe a picosecond non-thermal response of the CDW
order, characterized by a large enhancement of spatial coherence, nearly
doubling the CDW correlation length, while only marginally affecting its
amplitude. This ultrafast snapshot of the interaction between order parameters
demonstrates that their competition manifests inhomogeneously through
disruption of spatial coherence, and indicates the role of superconductivity in
stabilizing topological defects within CDW domains.Comment: 29 pages, 9 figures, Main text and Supplementary Material