Cu-NQR study for possible charge density wave state in CuO chain confined in insulating phase of Pr1−xYxBa2Cu3O7

We have performed NQR measurement on the Cu(1) site in the CuO chain in Pr1−xYxBa2Cu3O7 in order to investigate how the charge density wave (CDW) state observed previously in the end compound PrBa2Cu3O7 develops in going metallic phase with increasing x. The Cu(1)-NQR evidence for the CDW transition, that is the unusual broadening of the NQR spectrum after the critical divergence of the nuclear spin echo decay rate and/or nuclear spin-lattice relaxation rate, was found to be confined in x ≲ 0.5 being essentially insulating phase in Pr1−xYxBa2Cu3O7. The disappearance of the CDW state is owing to a loss of perfect one-dimensionality in the CuO chain when the CuO2 plane becomes metallic.