Effect of pointlike impurities on dx2-y2 charge-density waves in cuprate superconductors

Many cuprate superconductors possess an unusual charge- ordered phase that is characterized by an approximate dx2 - y2 intraunit cell form factor and a finite modulation wave vector q*. We study the effects of impurities on this charge- ordered phase via a single- band model in which bond order is the analog of charge order in the cuprates. Impurities are assumed to be pointlike and are treated within the self- consistent t- matrix approximation. We show that suppression of bond order by impurities occurs through the local disruption of the dx2 - y2 form factor near individual impurities. Unlike d- wave superconductors, where the sensitivity of Tc to impurities can be traced to a vanishing average of the dx2 - y2 order parameter over the Fermi surface, the response of bond order to impurities is dictated by a few Fermi surface " hotspots." The bond order transition temperature Tbo thus follows a different universal dependence on impurity concentration ni than does the superconducting Tc. In particular, Tbo decreases more rapidly than Tc with increasing ni when there is a nonzero Fermi surface curvature at the hotspots. Based on experimental evidence that the pseudogap is insensitive to Zn doping, we conclude that a direct connection between charge order and the pseudogap is unlikely. Furthermore, the enhancement of stripe correlations in the La- based cuprates by Zn doping is evidence that this charge order is also distinct from stripes.