We study the momentum and frequency dependences of the dynamical spin susceptibility in the superconducting state of bilayer cuprate superconductors. We show that there exists a resonance mode in the odd as well as the even channel of the spin susceptibility, with the even mode being located at higher energies than the odd mode. We demonstrate that this energy splitting between the two modes arises not only from a difference in the interaction, but also from a difference in the free-fermion susceptibilities of the even and odd channels. Moreover, we show that the even resonance mode disperses downward at deviations from Q= (π,π). In addition, we demonstrate that there exists a second branch of the even resonance, similar to the recently observed second branch (the Q* mode) of the odd resonance. Finally, we identify the origin of the qualitatively different doping dependence of the even and odd resonances. Our results suggest further experimental tests that may finally resolve the longstanding question regarding the origin of the resonance peak.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - May 29 2007|