Electronic spin susceptibilities and superconductivity in HgBa$_{2}$CuO$_{4+\delta}$ from nuclear magnetic resonance

TL;DR

This study uses NMR to identify three distinct spin susceptibilities in HgBa$_{2}$CuO$_{4+eta}$, revealing complex magnetic behaviors related to pseudogap phenomena and superconductivity.

Contribution

It uncovers a previously undetected third spin susceptibility and characterizes the temperature dependence of multiple spin components in the material.

Findings

Identification of two known spin susceptibilities with distinct temperature behaviors.

Discovery of a third, previously undetected spin susceptibility that changes sign near optimal doping.

Evidence suggesting the third susceptibility may result from coupling between the other two or be a separate component.

Abstract

Nuclear magnetic resonance (NMR) experiments on single crystals of HgBa$_{2}$CuO$_{4+\delta}$ are presented that identify two distinct temperature-dependent spin susceptibilities: one is due to a spin component that is temperature-dependent above the critical temperature for superconductivity ($T_{\rm c}$) and reflects pseudogap behavior; the other is Fermi-liquid-like in that it is temperature independent above $T_{\rm c}$ and vanishes rapidly below $T_{\rm c}$. In addition, we demonstrate the existence of a third, hitherto undetected spin susceptibility: it is temperature independent at higher temperatures, vanishes at lower temperatures (below $T_0\neq T_{\rm c}$), and changes sign near optimal doping. This susceptibility either arises from the coupling between the two spin components, or it could be given by a distinct third spin component.