Magnetic susceptibility of optimally doped HgBa$_{2}$CuO$_{4+\delta}$

TL;DR

This study measures the spin susceptibility of optimally doped HgBa$_{2}$CuO$_{4+\delta}$ and compares it with La$_{2-x}$Sr$_{x}$CuO$_{4}$, revealing differences in the Stoner enhancement factor and challenging existing theoretical models.

Contribution

It provides the first detailed comparison of spin susceptibility and Stoner enhancement between Hg1201 and LSCO, highlighting discrepancies with current theories.

Findings

Hg1201 has a similar normal-state spin susceptibility to LSCO.

The Stoner enhancement factor is larger in Hg1201 than in LSCO.

The correlation of the enhancement factor contradicts recent theoretical predictions.

Abstract

The magnitude of the powder spin susceptibility of an optimally doped superconductor HgBa$_2$CuO$_{4+\delta}$ (Hg1201) in the normal state is found to be nearly the same as that of La$_{2-x}$Sr$_{x}$CuO$_{4}$ near the optimally doped level. The Stoner enhancement factor of Hg1201 is larger than that of La$_{2-x}$Sr$_{x}$CuO$_{4}$. The magnitude correlation of the Stoner enhancement factor is inconsistent with the effect of the recent theoretical Coulomb repulsion between 3$d$ electrons and that of the superexchange intereraction of a charge transfer type.