Zn-Neighbor Cu NQR in Zn-Substituted YBa2Cu3O7-d and YBa2Cu4O8

TL;DR

This study investigates local electronic states near Zn impurities in YBa2Cu3O7-d and YBa2Cu4O8 using Cu NQR spectra, revealing enhanced magnetic correlations near Zn and more pronounced inhomogeneity in underdoped samples.

Contribution

The paper provides the first detailed NQR analysis of Zn-neighbor Cu sites in both optimally doped and underdoped YBa2Cu3O7-d and YBa2Cu4O8, highlighting local magnetic enhancement.

Findings

Shorter relaxation time near Zn indicates local magnetic enhancement.

Zn induces more inhomogeneous magnetic response in underdoped YBa2Cu4O8.

Satellite signals are assigned to Zn-neighbor Cu NQR lines.

Abstract

We studied local electronic states near Zn in optimally doped YBa$_2$(Cu$_{1-x}$Zn_x)$_3$O$_{7-\delta}$ and underdoped YBa$_2$(Cu$_{1-x}$Zn_x)$_4$O$_8$ via satellite signals of plane-site Cu(2) nuclear quadrupole resonance (NQR) spectra. From the relative intensity of Cu NQR spectra, the satellite signals are assigned to Zn-neighbor Cu NQR lines. The Cu nuclear spin-lattice relaxation time of the satellite signal is shorter than that of the main signal, which indicates that the magnetic correlation is locally enhanced near Zn both for the underdoped and the optimally doped systems. The pure YBa$_2$Cu$_4$O$_8$ is a stoichiometric, homogenous, underdoped electronic system; nevertheless, the Zn-induced inhomogeneous magnetic response in the CuO$_2$ plane is more marked than that of the optimally doped YBa$_2$Cu$_3$O$_{7-\delta}$.