Strong-coupling Effects in cuprate High-$T_c$ Superconductors by magnetooptical studies

Signatures of strong coupling effects in cuprate high-$T_c$ superconductors have been authenticated through a variety of spectroscopic probes. However, the microscopic nature of relevant excitations has not been agreed upon. Here we report on magneto-optical studies of the CuO${}_2$ plane carrier dynamics in a prototypical high-$T_c$ superconductor YBa$$Cu${}_3$O${}_y$ (YBCO). Infrared data are directly compared with earlier inelastic neutron scattering results by Dai $\mathit{\text{et}}\mathit{\text{al}}$. [Nature (London) $\mathbf{\text{406}}$, 965 (2000)] revealing a characteristic depression of the magnetic resonance in H $\parallel$ $\mathit{\text{c}}$ field less than 7 T. This analysis has allowed us to critically assess the role of magnetic degrees of freedom in producing strong coupling effects for YBCO system.