Magnetic resonance in the model high-temperature superconductor HgBa ₂CuO_4+δ

Inelastic neutron-scattering measurements of single- CuO₂-layer HgBa₂ CuO_4+δ reveal an antiferromagnetic resonance with energy ω_r =56meV (≈6.8 k_BT_c) below the superconducting transition temperature T_c ≈96K. The resonance is energy-resolution limited and exhibits an intrinsic momentum width of about 0.2 Å^-1, consistent with prior work on several other cuprates. The rather large value of ωr is identical to the characteristic energy of the electron-boson spectral density obtained from recent optical conductivity work, consistent with the notion that the charge carriers are strongly coupled to magnetic fluctuations.