Electronic spin susceptibilities and superconductivity in HgBa2CuO4+δ from nuclear magnetic resonance

Nuclear magnetic resonance (NMR) experiments on single crystals of HgBa₂CuO₄+δ 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 (Tc) and reflects pseudogap behavior; the other is Fermi-liquid-like in that it is temperature independent above Tc and vanishes rapidly below Tc. In addition, we demonstrate the existence of a third spin susceptibility: It is temperature independent at higher temperatures, vanishes at lower temperatures (below T0≠Tc), 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. Recent susceptibility data on single crystals support its presence in most cuprates.