Cu hyperfine coupling constants of HgBa$_{2}$Ca$_{}$Cu$_{2}$O$_{6+\delta}$

TL;DR

This paper estimates the hyperfine coupling constants of copper in a high-temperature superconductor using nuclear magnetic resonance data to understand the nature of ultraslow magnetic or electric fluctuations affecting nuclear spin coherence.

Contribution

It provides the first estimation of $^{63}$Cu hyperfine coupling ratios in HgBa$_2$CaCu$_2$O$_{6+ extdelta}$ from relaxation and Knight shift anisotropies, shedding light on slow fluctuation origins.

Findings

Hyperfine coupling ratios were estimated from NMR data.

Ultraslow fluctuations may originate from magnetic or electric sources.

Results suggest fluctuations are centered around wave vector q=0.

Abstract

We estimated the ratios of $^{63}$Cu hyperfine coupling constants in the double-layer high-$T_\mathrm{c}$ superconductor HgBa$_2$CaCu$_2$O$_{6+\delta}$ from the anisotropies in Cu nuclear spin-lattice relaxation rates and spin Knight shifts to study the nature of the ultraslow fluctuations causing the $T_2$ anomaly in the Cu nuclear spin-echo decay. The ultraslow fluctuations may come from uniform magnetic fluctuations spread around the wave vector $q$ = 0, otherwise the electric origins.