Crossover from inelastic magnetic scattering of Cooper pairs to spin-wave dispersion produces low-energy kink in cuprates

We present GW based self-energy calculations for the state of coexisting spin-density wave and d-wave superconductivity in a series of cuprate superconductors. In these systems, the spin resonance spectrum exhibits the typical `hour-glass' form, whose upward and downward dispersion branches come from the gapped spin-wave and magnetic scattering of Cooper pairs, respectively. We show that the crossover between these two different dispersion features leads to an abrupt change in slope in the quasiparticle self-energy, and hence the low-energy kink commences in the single-particle quasiparticle spectrum. The calculated electron-bosonic coupling strength agrees well with experimental data as a function of temperature, doping and material. The results demonstrate that the electronic correlations dominate the quasiparticle spectra of cuprates near the low-energy kink, suggesting a relatively smaller role for phonons in this energy range.