  The competition between superconductivity and charge density wave (CDW) order
in underdoped cuprates has now been widely reported, but the role of disorder
in this competition has yet to be fully resolved. A central question is whether
disorder sets the length scale of the CDW order, for instance by pinning charge
density fluctuations or disrupting an otherwise long range order. Using
resonant soft x-ray scattering, we investigate the sensitivity of CDW order in
YBa$_2$Cu$_3$O$_{6+x}$ (YBCO) to varying levels of oxygen disorder. We find
that quench cooling YBCO$_{6.67}$ (YBCO$_{6.75}$) crystals to destroy their o-V
and o-VIII (o-III) chains decreases the intensity of the CDW superlattice peak
by a factor of 1.9 (1.3), but has little effect on the CDW correlation length,
incommensurability, and temperature dependence. This reveals that while
quenched oxygen disorder influences the CDW order parameter, the spatial extent
of the CDW order is insensitive to the level of quenched oxygen disorder and
may instead be a consequence of competition with superconductivity.

Superconductivity;Strongly Correlated Electrons