Nuclear spin-spin coupling in La_{2-x}Sr_{x}CuO_{4} studied by stimulated echo decay

TL;DR

This study uses stimulated echo decay in copper NQR experiments to analyze spin-spin coupling in high-temperature superconductors, revealing temperature-independent relationships in La_{2-x}Sr_{x}CuO_{4}.

Contribution

It introduces a quantitative model combining spin-lattice relaxation and nuclear spin-spin coupling effects to interpret NQR data in superconductors.

Findings

T_{1}T/T_{2G} is temperature-independent in La_{2-x}Sr_{x}CuO_{4}

The model accurately describes experimental results in Y-based compounds

Extracted T_{2G} values for LSCO using the model

Abstract

We have performed copper NQR experiments in high temperature superconductors YBa_{2}Cu_{4}O_{8}, YBa_{2}Cu_{3}O_{7}, and La_{2-x}Sr_{x}CuO_{4} (x=0.12 and 0.15), using the stimulated echo technique. The stimulated echo intensity is analyzed by a model that includes the spin-lattice relaxation process (T_ {1 }-process) and the fluctuating local field due to nuclear spin-spin coupling. The model gives quantitative account of the experimental results in Y-based compounds using the known values of 1/T_{1} and 1/T_{2G}, the gaussian decay rate of the spin echo intensity. The same model applied to LSCO enables us to extract the value of T_{2G}. Our results indicate that T_{1}T/T_{2G} is independent of temperature, implying that the dynamic exponent is one in La_{2-x}Sr_{x}CuO_{4}.