Energy of the bosonic kinks in the quasiparticle spectrum of cuprate superconductors

Kinks seen in the renormalized electronic dispersion curves of the cuprates have been widely interpreted as due to coupling to bosonic excitations. The relationship between boson energy and the kink position can depend on temperature, the state of the electronic system, superconducting or normal, as well as on the shape of the underlying electron-boson interaction spectral density. Only in the unrealistic case of a Dirac delta-function spectral density does the kink energy correspond to the sum of the boson energy plus the superconducting gap.