The discovery of high-T_c superconductivity in cuprates has motivated extensive studies on the two-dimensional square-lattice systems. A key challenge is to understand the magnetic ground state of the parent phase from which superconductivity emerges upon carrier doping.

To address this issue, we recently performed resonant inelastic x-ray scattering (RIXS) experiments on Mott insulating cuprates to study the magnetic excitations which entail properties of the ground state. In combination with theoretical calculations, we reveal that quantum fluctuations—stemming from magnon interactions—have prominent influence on the magnetic ground state, manifested by the magnon renormalization. Our results suggest that the cuprate compound SrCuO₂ with moderate correlation strength and strong quantum fluctuations is a unique starting point for the exploration of novel magnetic ground states beyond the Mott physics.

This work has been recently published in Nature Communications (Wang, Q., Chan, Y. et al. Magnon interactions in a moderately correlated Mott insulator. https://doi.org/10.1038/s41467-024-49714-y).