Orientation of the intra-unit-cell magnetic moment in the high-Tc superconductor HgBa2CuO$_{4+{\delta}}$

Understand

Polarized-neutron diffraction experiments (PND) have revealed that the pseudogap state of the cuprates exhibits unusual intra-unit-cell (IUC) magnetism.

• At a qualitative level, the data indicate a moment direction that is neither perpendicular nor parallel to the CuO2 layers, yet an accurate measurement of a structurally simple compound has been lacking.
• Here we report PND results with unprecedented accuracy for the IUC magnetic order in the simple-tetragonal single-CuO$_2$-layer compound HgBa2CuO$_{4+{\delta}}$.
• At the transition temperature, we find evidence for magnetic critical scattering.