Impurity induced Local Magnetism and Density of States in the superconducting state of YBa2Cu3O7

TL;DR

This study investigates how nonmagnetic Zn and magnetic Ni impurities affect local magnetism and electronic states in the superconducting YBa2Cu3O7, revealing impurity-induced polarization and density of states modifications.

Contribution

It provides detailed experimental insights into impurity effects on local magnetism and density of states in high-Tc superconductor YBa2Cu3O7, using NMR and comparing with STM results.

Findings

Zn and Ni induce staggered paramagnetic polarization extending about 3 unit cells.

Zn induces a local density of states near the Fermi Energy that decays over about 3 cells.

The magnitude of the density of states decreases sharply with increasing temperature.

Abstract

Oxygen NMR is used to probe the local influence of nonmagnetic Zn and magnetic Ni impurities in the superconducting state of optimally doped high Tc YBa2Cu3O7. Zn and Ni induce a staggered paramagnetic polarization, similar to that evidenced above Tc, with a typical extension xi=3 cell units for Zn and xi>=3 for Ni. In addition, Zn is observed to induce a local density of states near the Fermi Energy in its neighbourhood, which also decays over about 3 cell units. Its magnitude decreases sharply with increasing temperature. This allows direct comparison with the STM observations done in BiSCO.