Analysis of the elementary excitations in high-T(c) cuprates: explanation of the new energy scale observed by angle-resolved photoemission spectroscopy.

We analyze the energy and momentum dependence of the elementary excitations in high- T(c) superconductors resulting from the coupling to spin fluctuations. As a result of the energy dependence of the self-energy Sigma(k,omega), characteristic features occur in the spectral density explaining the "kink" in recent angle-resolved photoemission spectroscopy experiments. We present results for the spectral density A(k,omega) for the feedback of superconductivity on the excitations, and for the superconducting order parameter Delta(k,omega). These results relate also to inelastic neutron scattering and tunneling experiments and shed important light on the essential ingredients a theory of the elementary excitations in the cuprates must contain.