Self energy effects in the cuprates

Optical spectroscopy and angle resolved photoemission have replaced tunneling spectroscopy as techniques that yield the best data on the self energy of the charge carriers in new superconductors. We review the most recent results of self-energy spectroscopy for several cuprate superconductors. We show that the self energy is determined by two channels of bosonic excitations, a sharp peak and a continuous background. Both channels appear to be of magnetic origin, the sharp mode is associated with the so-called 41 meV neutron resonance that appears only at low temperatures, a few tens of degrees above the superconducting transition temperature in underdoped materials, while the continuous background has a temperature independent spectral function.