Neutron resonance in high-T-c superconductors is not the pi particle - art. no. 144507

We discuss the interplay of particle-particle and particle-hole spin-triple t channels in high-T-c superconductors using a quasiparticle dispersion mot ivated by angle-resolved photoemission. Within a generalized random-phase a pproximation, we find a well-defined antibound state of two holes, the pi r esonance of Demler and Zhang, as well as a bound state of a particle and a hole, the spin exciton. We show that the energy of the pi resonance always exceeds 2 Delta, twice the maximum d-wave gap, therefore the neutron resona nce observed in the cuprates around energy Delta is most likely a spin exci ton. At the same time, we speculate that the pi particle can exist at highe r energies and might be observed in neutron scattering around 100 meV.