Magnetic resonance in the cuprates -- exciton, plasmon, or \pi-mode
  We re-analyzed the issue whether the resonance peak observed in neutron scattering experiments on the cuprates is an exciton, a \pi-resonance, or a magnetic plasmon. We considered a toy model with on-cite Hubbard U and nearest-neighbor interactions in both charge and spin channels. We found that the resonance is predominantly an exciton, even if magnetic interaction is absent and d-wave pairing originates from attractive density-density interaction. Our results indicate that one cannot distinguish between spin and charge-mediated pairing interactions by just looking at the resonance peak in the dynamic spin susceptibility. 
Zhihao Hao, Andrey V. Chubukov