Aspects of spin fluctuation scenario of superconductivity in high-T_c cuprates:
Resonant spin excitations and kink feature

Ilya Eremin

Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany

I. Eremin, D.K. Morr, A. V. Chubukov, D. Manske K. H. Bennemann, and M. R. Norman While it seems established that the resonance peak is a universal feature of the high-temperature superconductors, its origin, its role for the pairing process, and the effects arising from its interactions with electrons are still intensively debated. Furthermore, recent inelastic neutron scattering (INS) experiments on YBa2Cu3O6.85 in the superconducting (SC) state detected a new resonant magnetic excitation at incommensurate momenta, but at frequencies larger than (Q). In this talk within spin-fluctuation-mediated Cooper-pairing scenario I will address the feedback effect of superconductivity on the dynamical spin susceptibility and the elementary excitations. In particular, we show that the new resonance mode is indeed a spin exciton that emerges below Tc due to a feedback effect on the collective spin excitations arising from the opening of the SC gap in a dx2?y2 superconductor. Then we analyze self-consistently the pronounced momentum and frequency dependence of the self-energy originating from scattering of the quasiparticles on spin fluctuations and discuss its consequences for the ARPES data.