Origin of the unusual strong suppression of low frequency antiferromagnetic fluctuations in underdoped HgBa$_2$CuO$_{4+\delta}$

TL;DR

This paper explains the unusual suppression of low-frequency antiferromagnetic fluctuations in underdoped HgBa$_2$CuO$_{4+\delta}$, attributing it to symmetric oxygen doping and strong superexchange interactions, supported by a theoretical model.

Contribution

It introduces a theoretical model that accounts for the suppressed magnetic inhomogeneity and unique magnetic modes in underdoped HgBa$_2$CuO$_{4+\delta}$, highlighting the role of symmetric doping.

Findings

Suppressed magnetic inhomogeneity in HgBa$_2$CuO$_{4+\delta}$

Presence of weakly dispersive magnetic modes

Strong superexchange interaction due to symmetric O-doping

Abstract

Generally strong charge and magnetic inhomogeneities are observed in NQR/NMR experiments on underdoped cuprates. It is not the case for the underdoped HgBa$_2$CuO$_{4+\delta}$, the most symmetric and highest T$_c$ single layer cuprate, whose magnetic inhomogeneity is strongly suppressed. Also neutron scattering experiments reveal a unique pair of weakly dispersive magnetic modes in this material. We propose that these special properties stem from the symmetric positioning of the O-dopants between adjacent CuO$_2$ layers that lead to a strong superexchange interaction between a pair of hole spins. In this Letter we present a theoretical model, which gives a consistent explanation to the anomalous magnetic properties of this material.