Cu-NQR study for possible charge density wave state in CuO chain confined in insulating phase of Pr 1− xY xBa 2Cu 3O 7

Abstract

We have performed NQR measurement on the Cu(1) site in the CuO chain in Pr 1− x Y x Ba 2Cu 3O 7 in order to investigate how the charge density wave (CDW) state observed previously in the end compound PrBa 2Cu 3O 7 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 Pr 1− x Y x Ba 2Cu 3O 7. The disappearance of the CDW state is owing to a loss of perfect one-dimensionality in the CuO chain when the CuO 2 plane becomes metallic.