High-energy kink in high-temperature superconductors

Photoemission studies show the presence of a high energy anomaly in the observed band dispersion for two families of cuprate superconductors, Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{4+\delta }$and La$_{2-x}$Ba$_{x}$CuO$_{4}$. The anomaly, which occurs at a binding energy of approximately 340 meV, is found to be doping and momentum independent. The magnitude of the effect is momentum dependent. Scattering from short range or nearest neighbour spin excitations is found to supply an adequate description of the observed phenomena.