Slow transverse relaxation of the Zn-neighbor Cu nuclear spins in YBa2(Cu{1-x}Znx)4O8

An explanation is given for the recent observation in the plane-site Cu nuclear quadrupole resonance (NQR) study of a heavily Zn-substituted YBa$_2$(Cu$_{1-x}$Zn$_x$)$_4$O$_{8}$ that the Cu nuclear spin-spin relaxation time $T_{2G}$ near the impurity Zn is longer than that away from Zn. The long $T_{2G}$ of the Zn-neighbor Cu nuclear spins results from a distant coupling between only a few nuclear spins near Zn, which does not indicate the absence of local enhancement of the staggered spin susceptibility around Zn.